pipline always trigered surprisely - jenkins-pipeline

Question

I run 3 pipeline builds which need approval on jenkins where there are only 2 executors. So if the first and the second build are not approved, the third build will wait, meanwhile the strange things will happen that the third build will be triggered once per minute(I set scm poll "* * * * * "and these three builds all triggered by code commit). How can I fix this?
this is my pipeline script
pipeline{
agent any
stages{
stage('Build'){
steps{
echo 'Building123'
}
}
stage('Test'){
steps{
echo 'Testing12'
}
}
stage('Approve'){
steps{
script{
input message: 'Do you want to deploy?'
}
}
}
stage('Deploy-Staging1'){
steps{
echo 'Deploy-Staging1'
echo 'Deploy-Staging2'
}
}
stage('Deploy-Production'){
steps{
echo 'Deploy-Production'
}
}
}
}
build 47, 48 and 49 is triggered by commit, build50 and others are triggered accidentally
jenkins build screen
this is the polling log of build 54
Polling Log
View as plain text
This page captures the polling log that triggered this build.
Started on Feb 27, 2018 1:52:00 AM
Using strategy: Default
[poll] Last Built Revision: Revision f0a868f03cba928812b8505afbfd86034605f96e (origin/master)
> git --version # timeout=10
> git ls-remote -h https://github.com/yuzp1996/test-approve # timeout=10
Found 1 remote heads on https://github.com/yuzp1996/test-approve
[poll] Latest remote head revision on refs/heads/master is: 6a9a5f9ef27350be97978e225bef1dda7272f7ef
Done. Took 5.3 sec
Changes found