So, I think that there is somehow still a reference to potentially an old syncthing instance? On a number of the documents there are references to BGRPGB2, which isn’t one of the current instances. This may not be the cause, but not sure why it is happening.
The documents which are “out of sync” have a global availability of null, which I am guessing is the reason why it cannot sync, but the file is actually available at both machines.
So the next question is…
Why do these files have an availability of null?
this post mentions "availability": null, but says it is expected??