thanks for your fast feedback. I have not checked if there has been the GPS icon, but it could be the case that it was missing. I am using the nighly build of Cyanogenmod which is quite stable, so I was not linking this to the ROM. I am also using other tools for recording and there I have not recognised the same random recording stop.
Anyway I have deleted the 5.5.22 and I will only use the beta version from now onwards. I will monitor this and update you on the behavior.
If I am the only one experiencing this, then it is very likely to be my ROM.
br,
Matthias