Gradle task execution order doesn't seem to be garuanteed order - gradle

Question

I have written a tool OwnerFinder that does some annotation processing on some jars of an application. I need to expose this tool on TeamCity so have written a gradle script which performs following tasks
Extract the application zip file
Copy the application jars to a location build/appJars
compile tool OwnerFinder (keep the appJars in the classpath)
create jar of OwnerFinder
Run OwnerFinder(keep the appJars in the classpath)
(I need to keep the app jars in the class path because the annotation for which processing needs to be done is in those jars)
But somehow the order of the task is not guaranteed even after using dependsOn and mustRunAfter. The script fails either at
compilation task (where its not able to find the annotation in the dependencies)
or
run task where its not able to find the class OwnerFinder
but after 2nd or 3rd try it runs sucessfully. This makes me think that the gradle tasks are not executing as per order.
Following is my gradle script:-
apply from: 'http://some-gradle-util-script'
apply plugin: 'java'
def confs = ["someApplicationConf"]
confs.each { configurations.create it }
configurations { sources }
configureDownload('ivy', 'ivy-integrated')
dependencies {
def someApplicationVersion = '1.12.0.+'
someApplicationConf "com.soft:someApplication-sync:${someApplicationVersion}#zip"
compile 'com.google.guava:guava:16.0.1',
'com.google.code.gson:gson:2.2.2'
testCompile group: 'junit', name: 'junit', version: '4.11'
}
task unzip(type: Copy, dependsOn: clean) {
from zipTree(configurations.someApplicationConf.singleFile)
into "$buildDir/unzipped"
}
task copyJar(type: Copy, dependsOn: unzip) {
from "$buildDir/unzipped/modules"
into "$buildDir/op"
}
copyJar.mustRunAfter unzip
task compileOwnerFinder(type: JavaCompile, dependsOn: copyJar) {
FileCollection f = files(fileTree(dir: 'build/op', include: '*.jar').files, configurations.compile.files)
source = fileTree(dir: 'src', include: '**/*.java')
classpath = f
destinationDir = new File("$buildDir/classes/main")
}
compileOwnerFinder.mustRunAfter copyJar
task jarOwnerFinder(type: Jar, dependsOn: compileOwnerFinder) {
from files(sourceSets.main.output.classesDir)
}
task runOwnerFinder(type: Exec, dependsOn: jarR) {
def classpath = fileTree(dir: 'build/op', include: '*.jar').files + configurations.compile.files +
fileTree(dir: 'build/libs', include: '*.jar').files
commandLine "java", "-classpath", classpath.join(File.pathSeparator), "OwnerFinder"
}
runOwnerFinder.mustRunAfter jarOwnerFinder