did the guy de-wax and clean the area around wound,....is it falling out back to the bottom of the wound, did he seal it with some epoxy?
I'd suggest starting over...de-wax and clean the wound...all the way to the bottom. the roughen up the bottom and put a bit of epoxy to make sure it is sealed up...let dry.
The again roughen or hash up the dried epoxy and the ptex surrounding the wound...perhaps use a sharp wood chisel. This is because it will create a mechanical bond...like a lock and key.
Then when preparing to ptex...first briefly heat/warm up the wound with a propane torch. Followed up with flowing in the ptex....it might take a couple times to fill it in...but warm up the base around the wound.
After its filled in but still slightly warm, with a very sharp wood chisel....cut or shave it flat. Then let it cool down.
After its cooled down, again roughen up the repaired wound with some 80 grit sand paper....then clean it and get any grit out/off.
Lastly wax, scrape and buff.
At least thats generally what I do and it holds.