Hi SGador,
Thank you for the report. Unless this behavior was introduced by Castra Prime - in other words, ERM and original Castra got along fine - I have to categorize this as not a bug and something that likely won't be addressed without further info and user reports. This is a case of two "wacky" military overhaul mods not working together in the way you are looking for. If this is a substantial issue, I'd recommend posting the issue on the ERM side and asking them exclude Castra's surface from their changes.
If you have a more specific suggested fix or you're testing this against original Castra and seeing that it works there, please let me know and I'll take a deeper look. I'm also open to hearing if this is a wider issue (i.e. what the ERM/Castra Prime overlap is).
All the best,
-Erro
