When opening the same file in another terminal, micro behaves inconsistently

Description of the problem or steps to reproduce

Expected behavior: every time I try to open a file that is already open (and changed) in a different terminal, micro should warn me (I opened another issue #2978 which deals with the nature of the warning and the imho insufficient options micro offers to the user in this situation but this is unrelated).

Actual behavior: micro sometimes warns me when doing that, and sometimes it doesn't. When it doesn't, I may have (unknowingly) 2 conflicting buffers of the same file.

While testing, I have repeatedly reproduced the issue but I didn't manage to figure out what are the exact conditions which trigger this behavior. I think this may be related to me once pressing the 'i' (for ignore) while loading a 2nd buffer of the same file - then even if I close the file in both terminals and then open it again in 1st terminal and make some changes, micro will allow me to open that file in the 2nd terminal without the usual warning. That's my best theory right now. I do see that micro is keeping the "backup" file even when this happens, so I suppose there is some "flag" it sets [for a particular file?] which (when set) allows then to open 2 conflicting buffers. And that "flag" seemingly doesn't get reset, at least not every time.

Specifications

Commit hash: c2cebaa
OS: Debian
Terminal: xterm (SSH with mobaxterm)

Start by reproducing the cross-terminal file-opening scenario described on Debian, including pressing “i” while loading the second buffer. Compare cases where micro warns with cases where it does not, and inspect how the backup file and any associated state behave after both terminals close. Done means identifying the trigger and making repeated opens consistently warn.