1. Yes it COULD be but it is hard to say
2. It seems like the only other real possibility is a wiring issue between the ECM and TCM.
I haven't seen this particular problem before so I can't really give you a specific experience answer.
It looks like the TCM is losing communication from the ECM and setting a code then setting a code for a data parameter that it loses as a result.
The issue could be in either.
I have replaced more ECM's on those than TCMs but for a slightly different issue.
I don't have a definitive answer for you but those are some things to consider.