The cut out in the bolt is looking sharp and does not appear to be the problem. The hook of the extractor seems a little rounded off and I think that causes the slippage.
In a case like that I would check the long sliding bar of the extractor and see if I could kind of shim it up, i.e. put first a cut off from a .22 case underneath with some glue or a thin metal strip inside the bolt channel. I guess that bringing the extractor up higher will reduce risk of slippage. The extractor hook might need a little recontouring, too.
I have the chamber reamers and would also just ream the chamber by hand, very slightly. I have found a few early German Anschutz rimfire rifles to have tight chambers. Without the reamer, a Dremel with a bronze brush and polishing compound used carefully should not do harm.
Compare the hook with yours. In case of need, I can measure the height.