Okay, I tested it with my file were I originally started this run.
And luckily, I didn't import a file inbetween since I transferred it to another system, the Gantry Feeder thing happend and now. So I had a clear testing area.
I did start some new Runs since then, but the original Town stayed the same.
Sadly it happend basically the next day.
So it is either a bug or actually intended to happen between two Feeders after some time.
Since you confirmed you hadn't exported the file before it happend, we can rule this out as the source of the bug (if it is a bug)