Tremelo footswitch pop

[Toxophilite]

On one of my builds, an AB763 type  one deluxe reverb with 6G11 tremelo(who knew I would know what these numbers ^&$^% mean)


My footswitch for the reverb has started to make a pop or thunk when I switch it on or off. It's an epiphone amp footswitch I rewired and I've used it for a couple years on my super (I have 2 actually, one for reverb too) and now on this amp with no problem. It just started to make a pop/thunk...the beginning seemed to coincide with the addition of the reverb circuit I just finished however I can't be certain


If I swap the two (identical epiphone amp)pedals over, both pedals work fine on the reverb and pop on the tremelo circuit so it seems like a tremelo circuit issue rather than the pedal. and it just started happening


Any ideas?