Workaround found in comments down below

Active Choises Reference Parameter runs this groovy script:

import static groovy.io.FileType.DIRECTORIES
def users_path = new File("C:\\Windows\\SoftwareDistribution")
def folders = []users_path.traverse(type: DIRECTORIES, maxDepth: 0) {
    if (!(it.name == "_FIRED") && !(it.name =~ /^[0-9]/)) {
        folders.add(it.name)
    }
}
return folders 

It returns some folder names basically. There are hundreds of them in production so I used filtering for easier selection, but filtering doesn't work on Active Choises plugin version 2.8.7 and 2.8.8, however on 2.8.6 it works, so far I reverted to 2.8.6. Script still returns all the elements I expect it to, just filtering broke.

This is how it looks and what console returns: