I have the same head, same issue. If the amp is set to clean (gain low) this issue does not happen, but then what's the point of running such a nice amp clean 🙂
No reverb, settings are as follows
gain 12 oclock
bass 9/10 oclock
treble 12 oclock
brilliance 11 oclock
master volume 1 o'clock
ive tried the the low gain input as well, the effects loop issue is present using that input as well.