Help How to prevent people from duplicating mob spawners? to do this,, First you must have a silk touch pick. then there must be a mob spawner in a different faction. Break the spawner there... DUPE! T_T
That you tried running the FBasics plugin? It fixes some bugs and glitches, however it's not full proof.
Can you post a private video / steps of how to reproduce this to the plugin's issue tracker to get it properly fixed instead of just asking for a hacky fix that just puts a bandaid on a bullet hole please?