Something funny about UNDO

Noticed in Afrika Korps, not sure if it’s a global issue:

Played through some moves, changed my mind and used UNDO several times. I thought I had undone everything (went back to the first piece move) but then when I started looking at my alternate plan, I noticed that 3 pieces were stacked when they had all been on different squares before I undid anything…

Sounds quite like a situation I ran into some months back (also in AK, if that means anything) - but being unable to replicate the problem, trying to debug it seemed futile.