I've been playing MCE eternal 1.5, 1.12.2 and whenever a security terminal is connected to my ae2 network blocks will just straight up break dropping their contents into the world. I just watched all of my ME driver literally break in front of me dropping their drives into the world. The issue also happens with cables, me interfaces, molec assemblers, and every other native AE2 block.

I'm not entirely sure what else to provide. I had the entire network chunkloaded using FTButils. I also had a blank biometric id card with build privs in the security terminal.

Update: I put the security terminal on a separate sub network and the issue still happens.

You can try putting a blank biometrics card into the security terminal and allowing everything for it. Otherwise, it might give you trouble if any block in your network has not been placed by you (or in case of 1.12 it might have forgotten about the placement info).

I can't really help beyond that since we don't support 1.12 anymore, sorry.
You might try Prototype Trousers 1.12 Fork of AE2: https://github.com/PrototypeTrousers/Applied-Energistics-2