Hello,
I found very helpful people here so I’d like to give something back to the community by providing the solution for my problem. That is the least I can do.
It turned out to be a problem with using headphones that have a microfone build in. It is a decent one with on ear drivers and so on thought, but has this 3,5 mm, 4 contacts connector. The singer of our band used this and plugged it into a standard headphone adapter 3,5mm to 1/4" stereo to connect to the UR22C. This causes crazy phase canclelations. Unfortunately when I asked to try another pair of headphones she chooses the headphone of her mobile phone and guess what…same problem…of course 
Thanks
TonNiveau