No master CAN fault message

We have a system with MC43FS > MD5-10 > MC43FS layout. The MD5 display is central between the MC43's using the CAN in/out pins for connections. CAN terminations (software enabled) on both MC43 master and diagnostic busses (each MC43 module is end of line).

We had a fault where there was no comms on the master bus using APP IN/OUT between any of the 3 modules, just indicated red in IQAN design and state 'timeout' on the app in's. No error flash on the MC43 LED and no error message shown on the MD5.

We found that the master bus wired in the MD5 was the wrong way around (CAN high /CAN low incorrect), but it did not show this as an error, no logs suggested what the problem would be. I'm sure normally if this happens we get a bus error/ CAN fault shown on the screen, pointing us to where the problem may be, but this doesn't seem to have happened in our case. Could be helpful for future fault finding if it was available or showed a message?

IQAN Design 7.05.27.10982