UMC1820 : UMC 1820 and the reason of the return

The product is Behringer UMC1820 and the reason of the return is in the fact that the unit has shown itself to be unstable using the USB connection and would drop out after 1 to 20 min. and sometimes would not be recognised by the operating system. I have run the tests on 3 different computers ( win10, 8 and 7) using the drivers provided by the Behringer Music Group company and... no luck. For the 15 min. operation I've recorded a drum set with 8 mics and the sound was very good for the price. So, I guess that the problem might be in the particular unit that was sent to me and not with the UMC 1820 series 'cause I haven't seen that anyone else reported such an issue.