I found the solution for me:
First I used the UR22mkII with my ASUS N55SF Laptop without any issue ever. for months.
Then I upgraded my PC with a new motherboard/CPU and a new graphics card and connected the interface.
There I had drop outs pretty often especially while gaming, but also when just listening to music sometimes.
I tried powering the interface externally and got a quality USB cable but this didn’t help a lot either.
Then I got myself a new power supply. First a LC-Power. This already solved the drop out problem, but I had to exchange it because of noise.
Now I have a beQuiet 850W power supply.
I have since NEVER had any drop out anymore.
I really think you guys should consider a power supply, even if you are not on a limit power wise.
Hope this helps a few of you.