I created a local and global password.
In a shell step the password can be used successfully.
In the next build step of my build I have the Gradle plugin, the password arrives as asterisks.

As a work-around I have switched to use the MaskPassword plugin.

Test Script build.gradle:

task showGlobalEnv << {
println '\''Test match:'\'' + (System.env.TEST_ENV == 'T123')
System.env.TEST_ENV.each

}

Output from version 1.90 (successful):
Test match:true
T
1
2
3

Output from version 1.91 (failure):
Test match:false
*
*
*
*
*
*
*
*