In scenarios when you have destroyed the beacon the enemies just walk about. You can't fight them and they don't attach.
I can see those minions in the save, but I have no idea how they can end up in this state.
Their ability to take part in fights got disabled, this happens for example when units are put on props eg. torture,
but when ever they leave these props this is reset to normal.
Some error must have prevented their reset, but I do not know which.
A heads up that this is not necessarily caused by the Arcane Inhibitor, guessing Mighty Script, and not purely older levels. Encountered it on official maps(The Under Games+skirmish), and Custom Campaign (Squad Leader by Taktikus, third level) in which player is in possession mode and cannot build or cast spells. That level was created just a few days ago.
The affected units is shown in Debug Mode as "Unit is disabled!" under conditions, and there is no information in logs(For you to verify I've attached log, and a save from above Custom Campaign).
Updating this ticket to reflect that is currently pending our next triage pass.
In the end we found the cause:
https://support.brightrockgames.com/communities/1/topics/5131-defenses-not-attacking-and-not-being-attacked-either-near-core-undergames-build-v206f2
Save games however will still keep this issue but it wont happen again in a newly started game.