Terminal server Vantage sessions showing different users screen

I came in this morning & had this email. Is this a known TS issue that I just can't find?

Last night, for some reason, or computer screens would flip flop every so often. Just all of a sudden I would have 2 mills screen on 3 mill and Carl would have 3 mills screen on 2 mill. Just had to end activity and clock out then clock back in.