Help with feedback issue at venue

[r3vo1ution1991]

I've played at my friend's church a few times, and I've noticed that when I'm set up on a certain part of the stage, a few of the instruments/voices start getting picked up by my pickups (Humbucker-Single Coil/S/S Strat), and have even gotten feedback when in the 3/4/5 pickup position. This makes the other musicians sound like their running through my FX board, but it only seems to happen when I'm standing in a certain spot. I did try switching input jacks as well as electrical outlets, but where I'm set up is what seems to matter. I am in between two input jack floor boxes, and I thiiiinnnkkk it's the floor box in front of me causing this issue because this issue becomes more pronounced when I'm near that box (when I stand farther back I hear it much less, but I still have issues of getting feedback when using my single coils).

Is there any way to figure out what is causing this, or does anyone have any ideas? Unfortunately this church is fairly small and I don't believe the person who helped install the system is there anymore.

 

[r3vo1ution1991]

Clarifications (as well as a bump): My pickups are low-to-medium output pickups, everyone runs through in-ears (so no wedges), I'm not using a wireless unit, and the two most prominent people that I hear being run through my FX are the violin (who stands on the other side of the stage) and one of the vocalists (who stands about 7 ft in front of me).

 

[Mark-B]

Microphonic? ..Wax potting might help. Basically, you pull the pickups, soak them in hot wax, the pickup's internal parts quit vibrating which limits microphonic feedback.

 

[r3vo1ution1991]

Microphonic? ..Wax potting might help. Basically, you pull the pickups, soak them in hot wax, the pickup's internal parts quit vibrating which limits microphonic feedback.

Good suggestion! However this only happens at this church, I play at other locations (and have even played at the same church, but standing in a different spot) with none of these issues. Someone I talked to suggested it might be the hearing aid loop causing this issue, so I'm gonna look into that possibility.