MC41 losing CAN comms

We are using a MD4-7 and x2 MC41's on some of our machines (we actually wanted to use only x1 MC42 for these jobs but we are still waiting for the parts to arrive and have deadlines to meet so we are just using what we have available to get the job done)

But last night we started testing the machine and went through all of the procedures and functionality when all of a sudden an error appeared on the display telling me that one of the MC41 controller lost comms, but the other one was still fine and giving readings... So the 1st thing we tried to resolve this was typically switching the machine off and on, but this time there was no CAN comms at all.

We went though the wiring harness and made sure that everything was correct and the wiring was all good, so we then went and replaced both these controllers with new MC41's we had in stock, we plugged it in uploaded the software and the system was happy again with the new controllers and it is still working fine at this moment... So I took the 2 faulty MC41's to my office and connected it all together to try and diagnose the issue. 

Each time I tried uploading software (using IQANDESIGN 5.01 via ethernet) it kept on warning me about the incomplete system and that only the MD4-7 will be updated.

Eventually we switched from CAN-A to CAN-B only on the MC41's. but upon each attempt to upload the software, the same "incomplete system" warning appeared. 

So I just left it for a while and a few minutes later decided to just try again uploading once more. Well it worked all of a sudden and that is also a big problem, because I didn't change anything where I could say " there, that was the problem".

This is worrying us a bit, because we have no idea why this happened in the first place and secondly these machines are going to the middle of Africa... So this sort of thing must not happen at all!

I have only been using MD4's and MD3's with XA2's in the past without any problems at all, these are our first machines using the MC4x family and this is also the 1st time that I encountered any issues like this on IQAN.

Have anyone else experienced this before?  I have no idea why it failed or why it started to work again and this is definitely not the correct answer to give the person asking this question when there are deadlines to meet.

The other thing to mention also is the LED's on the controllers which blinked bright yellow 3 times then blinked dimmed yellow 3 times while it was not communicating. which also does not correspond with these fault codes in the manual. There was no RED LED blinking at all.