A wood dowel hammered into here? It looks more like a drilled and threaded hole with a tapered opening fitted nicely to match the taper on the bolt. Old wood drying and developing a crack is not unusual. Funny thing though, I just repaired a cue last night with three splits in it where the bumper pushes in. It is a very old well made cue. I don't think it's a Bushka, but it's certainly not a Taiwan. No way is that a Taiwan shaft, Bumper, Butt cap, Wrap, or ferule. Too many nice things to be a cheapo import. I look forward to seeing the results of the refinish. looking at the pictures again I can see tell the whole thing was sprayed over with a rattle can many moons ago.It's possible, but it looks like that other plastic
The buttsleeve is split, I bet there is a square wood dowel hammered in there
P.O.S. either.