@isladogs - great detective work. You even have the ear of MS being a current MVP. Any chance they're going to fix the problem?
Ha!
The bug has existed ever since the complex field types were added with Access 2007 so only 15 years so far!
That even exceeds issues such as the much more important 'monster bug' which is only 4 years old so far (and on the roadmap to fix) ....
I contacted the Access team about this particular bug last year and they were able to replicate it but stated it was low priority(!) for fixing.
I reminded them in January & got the same response.
To be fair, I agree that its an issue that is very obscure and has probably rarely arisen in all that time.
I suspect it will never be fixed whilst other much more pressing issues still need attention.
However, I've recently been in discussion with ex-MVP Ben Clothier about this issue
As I'm sure you're aware, Ben is far more knowledgeable than almost any other Access developer / MVP.
With some very helpful prompts from Ben, I believe I am very close to fully explaining the problem ... and I already have a solution!