I have seen this behavior as well, not really sure why.
I have also noticed when it is very cold outside, setting temp to 17/18degC is too warm, but if you go to 16 it blows clod air on both sides, so I have to set it to 16.5degC minimum....
Bluestone G30 ///
M Sport Auto (Current)
Alpine White F10 M Sport | 8 speed Sport Auto - Gone to Stud