According to @lucadeltodecso the XP is only stored for approximately a week. You might be losing XP doing this. I’m not sure if this affect XP still stored on the machine, or only XP that has been release from the machine to the beacon.
There are some very interesting posts in that thread…
This is correct, although “interact” can be simply looking at it long enough to force the status display.
The XP is collected to the beacon if another character (character B) interacts with the machine while you (character A) have an item crafting in it. Character A will then collect the XP to the character when they enter the beacon.
If Character A interacts with the machine first, the XP is collected to the character that moment.
If you are deep enough this doesn’t seem to matter. My old workshop was between my hub and one of my retail shops, and people would run over the roof (within three blocks of my coils/machines) all the time. It took me forever to figure this out due to sometimes logging in to no XP, sometimes logging in to some, and sometimes logging in to all my XP already being “in the beacon”.