I now understand how my relationships were pathological, however, I do not understand your new relationship fully. If I can attempt to clarify the logic maybe that would help.
The form should show:
ECR#1 was written by Kirt, it adds partnumber1 and deletes partnumber2 from modelA & modelB. (It should show the add partnumber1 and delete partnumber2, as well as modela & modelb)
ECR#2 was written by David, it changes partnumber3 from modelA. (It should show only the change of modelA)
The form or any variation I have tried with it will not display this info. The relationships do not show it either.
Once again, thank you very much for sharing your extensive knowledge with neophites like myself.