Reply to My 1st snag with S4/TP2 on Windows

If I'm recording a mix - using the INTERNAL recording option -
- using S4 soundcard
- headphone monitoring
- pre-analyzed playlist
- minimal EFX
At some point - round about 18min - EVERY TIME - I get a brief sound drop-out. Anything from barely audible to up to a second's silence. Set-up runs FAULTLESS before and after that point.

Any one got any ideas please?

Thank you.