My guess would be a wood-boring beetle, but I don’t know what is native to your region. Those little rectangular dark droppings look like boring beetle droppings to me too.
Wow ! That is one nasty little wood borer doing his bad deeds !!
I’m new to this and still learning, but being an intruder, why wouldn’t the bees kill it?
They might try, but if it can hide somewhere that they can’t reach it, it could get away. That hole looks about 3mm to me - too small for a bee to get into.
It looks like they tried to seal it in. Probably corralled it there and then without any other option bored straight down to get away. If you know the beetle is still in there maybe pour a little molten bees wax in there to seal him in for good.
Or clean it out with a toothpick
And then seal the bug in with dental amalgam!!!