Grails ClassNotFoundException only in one subproject - gradle

Question

I'm pulling my hair over this crazy problem that doesn't make any sense to me. I have a large Grails 4 project with multiple sub-projects. In two of these subprojects, let's call them A and B, I have a dependency to a plugin (non-public plugin): implementation group: 'dokumentlager', name: 'dokumentlager-grails4-plugin', version: "5.4.1".
This dependency has two transitive dependencies, as seen in the External Libraries list in IntelliJ:
In sub-project B a class from "dokumentlager-api" is used in a Service and imported like so:
import dokumentlager.api.Indholdstype
This gives no errors and I can start B normally.
However, in sub-project A I also import the same class and use in a Service, but there I get a ClassNotFoundException:
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'grailsApplicationPostProcessor' defined in dk.erst.plandata.integration.Application: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [grails.boot.config.GrailsApplicationPostProcessor]: Factory method 'grailsApplicationPostProcessor' threw exception; nested exception is org.grails.core.exceptions.GrailsRuntimeException: Failed to introspect class: class dk.erst.plandata.integration.faelleskomponenter.DokumentlagerPluginService
at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:657)
at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:485)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1341)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1181)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:207)
at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:119)
at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:707)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:533)
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:405)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:315)
at grails.boot.GrailsApp.run(GrailsApp.groovy:99)
at grails.boot.GrailsApp.run(GrailsApp.groovy:485)
at grails.boot.GrailsApp.run(GrailsApp.groovy:472)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:101)
at org.codehaus.groovy.runtime.callsite.StaticMetaMethodSite$StaticMetaMethodSiteNoUnwrapNoCoerce.invoke(StaticMetaMethodSite.java:149)
at org.codehaus.groovy.runtime.callsite.StaticMetaMethodSite.call(StaticMetaMethodSite.java:89)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:47)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:115)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:135)
at dk.erst.plandata.integration.Application.main(Application.groovy:11)
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [grails.boot.config.GrailsApplicationPostProcessor]: Factory method 'grailsApplicationPostProcessor' threw exception; nested exception is org.grails.core.exceptions.GrailsRuntimeException: Failed to introspect class: class dk.erst.plandata.integration.faelleskomponenter.DokumentlagerPluginService
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185)
at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:652)
... 30 common frames omitted
Caused by: org.grails.core.exceptions.GrailsRuntimeException: Failed to introspect class: class dk.erst.plandata.integration.faelleskomponenter.DokumentlagerPluginService
at grails.core.ArtefactHandlerAdapter.isArtefact(ArtefactHandlerAdapter.java:129)
at grails.core.DefaultGrailsApplication.addArtefact(DefaultGrailsApplication.java:774)
at grails.boot.config.GrailsApplicationPostProcessor.performGrailsInitializationSequence(GrailsApplicationPostProcessor.groovy:112)
at grails.boot.config.GrailsApplicationPostProcessor.initializeGrailsApplication(GrailsApplicationPostProcessor.groovy:94)
at grails.boot.config.GrailsApplicationPostProcessor.setApplicationContext(GrailsApplicationPostProcessor.groovy:231)
at grails.boot.config.GrailsApplicationPostProcessor.<init>(GrailsApplicationPostProcessor.groovy:78)
at grails.boot.config.GrailsAutoConfiguration.grailsApplicationPostProcessor(GrailsAutoConfiguration.groovy:70)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
... 31 common frames omitted
Caused by: java.lang.NoClassDefFoundError: dokumentlager/api/Indholdstype
at dk.erst.plandata.integration.faelleskomponenter.DokumentlagerPluginService.<clinit>(DokumentlagerPluginService.groovy:23)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:348)
at org.codehaus.groovy.runtime.callsite.CallSiteArray$1.run(CallSiteArray.java:67)
at org.codehaus.groovy.runtime.callsite.CallSiteArray$1.run(CallSiteArray.java:64)
at java.security.AccessController.doPrivileged(Native Method)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.createCallStaticSite(CallSiteArray.java:64)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.createCallSite(CallSiteArray.java:161)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:47)
at org.codehaus.groovy.runtime.callsite.StaticMetaMethodSite.call(StaticMetaMethodSite.java:94)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:119)
at grails.plugins.quartz.JobArtefactHandler.isArtefactClass(JobArtefactHandler.groovy:62)
at grails.core.ArtefactHandlerAdapter.isArtefact(ArtefactHandlerAdapter.java:125)
... 42 common frames omitted
Caused by: java.lang.ClassNotFoundException: dokumentlager.api.Indholdstype
at java.net.URLClassLoader.findClass(URLClassLoader.java:387)
at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:355)
at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
... 55 common frames omitted
So far, I've tried:
Adding "dokumentlager-api" as an explicit dependency
Invalidated caches in IntelliJ
Manually deleted all caches in .gradle/
Re-cloned my repository
Reinstalled IntelliJ
How is it possible that with the same setup this gives me an error in project A but not in project B?! I should add that we have another developer that CAN start A locally... so it seems to be a very local issue...
PS: I'm using gradle 5.2
EDIT
I ran a build scan for my two sub-projects and they have the exact same dependencies in borth compileClasspath and runtimeClasspath: