To those experiencing weired face exchange with the merc swapping feature (CTRL + left / CTRL + right):

I have a feeling that this is somehow related to interrupts. Could you please check and confirm (or not).

When it happened in my game that a merc was moved away from the spot where I put him it was during an interrupt. I could see that my Squad[0][] array had the wrong order but I don't know why. For example merc 4 was now in position 0. This is retained during save/load. Also gTeamPanel has the same wrong sort order. The only way to fix Squad and gTeamPanel is to reassign the group but at some point it gets a wrong sort order again.

First thing I will do is to issue a sort command after swapping mercs so that the Squad array has the correct order but this will not fix the issue with interrupts.