Game losing track of minion location/"teleporting" across the map
I have experienced infrequent instances where when setting a "rally all" flag that involves a large number of minions, sometimes a (seemingly) random minion will be moved to a far-off location that always ends up in enemy territory, so the first time I notice anything amiss is a "minion lost" message out of nowhere.
This sounds very strange indeed.
Do you know how many minions you had at the time? Was there a particular level you were playing? Was it a particular minion that presented with this behaviour? When you say the unit teleported did it arrive roughly at the location of the rally flag?
Cheers,
Lee