Thanks for the bug report!
This is most likely an incompatibility with the Moulder's Menagerie mod. There is a scripting conflict with my Underground Advance ability and the Burrowing Behemoth from that mod that I am currently trying to figure out how to resolve. I suspect it might need a submod, though.
If you do not have this mod installed, then I would be very interested to hear if any other mods out there are causing the same issue.

Thanks again!

I do have Moulder's Menagerie installed, and they do have a unit that has a similar function so I imagine that's the case, yeah.

The issue has been fixed! If you update both mods, then they should work fine together!

Just a heads up, encountered this same issue. Also have moulders meangerie. Units were invisible, healed infinitely, and their unit cards appeared way up in the sky.

I would try updating both mods. An easy way to do force this to happen is unsubscribe from both and then resubscribe.
I have both installed and it is not giving that behavior for me. Let me know if you still have any issues! Hope that helps!