I tried this manual read in putty, and same thing happens there.
I’m not sure if this is related to my windows installation (not likely, random error), PC-hardware or worst case ThermIQ-hardware.
Anyway a disable/enable of serial-interface or restart of the computer solves this temporary.
My so far work-around is a scheduled reboot every 30mins, no lockups and computer boots in 1 min.
Seems I’m missing only 1-3 measurements during this. 🙂