XC43 System mismatch with Newer MD4-7

I've been having some very strange issues today with XC43 "System mismatch" errors on a system with an MD4-7 and XC43. We're on IQANdesign 6.01.6. There's 1 XC43 with address 1 on CAN-C. When I load this program on new MD4-7 and XC43 I get the XC43 "System mismatch" error and the XC43 has internal state "Failed 306". The amber LED continuously blinks very quickly.

When I move the XC43 to CAN-A or CAN-B and reload the program, everything works. I then move the XC43 back to CAN-C, reload the program, and everything works.

Having the XC43 on CAN-D seems to result in the same "System mismatch" error.

We've used this same program and these same modules on many other machines without this issue, so looking closer at the MD4-7-T1E2 modules I was testing with, it seems like something changed with the modules with 2023 manufacture dates (2302040070 is the earliest SN that I experienced this issue with). All our modules that are later than 2208040660 don't seem to load the firmware onto the XC43 on CAN-C or CAN-D or something. 2208040660 and earlier have no problem operating the XC43 on CAN-C.

Did something change in the CAN-C and CAN-D ports on the MD4-7 suddenly sometime after SN: 2208040660 that they can no longer load firmware onto expansion modules? Or am I doing something wrong?

This could become a fairly serious issue with replacing XC43 modules in the field in the future. If CAN-C and CAN-D can't load firmware on the modules, we'd need to either reprogram the existing system or make sure the firmware is updated before it ships out. This isn't always easily done and kind of defeats the major advantage of expansion modules (forward/reverse compatibility without reprogramming). And if we can't use CAN-C/D for expansion modules, it severely limits their usefulness, since we're already advised not to use these buses for the diagnostic bus.