With the following commit:
4d66dc3 - Core: Split tfm_core.c into IPC and library model
The ConfigCoreIPC.cmake with Regression set to True is now giving the following error messages during runtime:
[Sec Error] Unauthorized service request!
[Sec Error] Security violation when calling secure API
This could be related to another issue that NXP has reported on the mailing list on a NULL pointer passed to tfm_thrd_context_switch(...) is causing a BusFault (I am not sure about that though at the moment, to be investigated further)