Razer Book 13 external Display

I have an issue with the Razer Book 13 when connected to an external monitor: A short flash/flicker appears from time to time. Tried to fix it the last 3 days (new graphic drivers, changed graphic settings, firmware update, factory reset, all other recommendations) nothing helped. I like the device very much but this issue is very annoying. I made a screenshot of the flash. The icons from the desktop appear for a short time on the right side. My monitor works fine with 3 other laptops.