Just until today I had the issue with the V5i opamp cutting off. I had no problem using the XD-05 on high gain but I never move the bass switch from the left position.
So I noticed this:
Bass on left position with high gain - working fine
Bass on right position with medium gain - working fine
Bass on right position with high gain - cut off
I own XD-05 with v5i op-amp and I too am having a problem with cutting off at high gain setting.
But for me it just cuts off at high gain, no matter whether the bass is switched on or not.