Water on top of stove

Must be coming in from somwhere around the chimney/flashing. Check that flashing was installed correctly

Put some high temp silicone on the seams of your class A pipe that is outside of the structure and around the ring that goes above the roof flashing.

Found exactly same issue couple years ago - walked in to find a small puddle on one corner of the stove. Turned out to be an issue with the way the roofers shingled over the edges on the bottom 1/2 of the the flashing (where shingles should have been under the flashing). Water got under and rode the top edge of one shingle, back under the flashing, and found its way down into the support box, dripped down onto the stove from there. Brand new roof, I was pi$$ed. It was hit and miss, took a good rain to push a few drips in, but it was just a bad install. My own DIY install several years prior never leaked a drop. So much for "pro's". Sorry for the rant, but hope the info helps. As mentioned, make sure the storm collar and seams are sealed (silicone) as a start.

Mice pee.

I had that problem years ago with Class A.
Turned out it was the vertical seams in the Class A and dripping down to the support box and then dripping down to the stove.
Try sealing the vertical seams and makes sure storm collar flashing etc are ok too.

If it was a cold/ not environmentaly controlled camp it could have been condensation too. You'd be surprised how much water can accumulate from condensation running down the pipe.

If you don't see anything wrong elsewhere its a good possibility