Hi Petr, thanks for reporting this with the very clear and easy to follow repro steps!

This was related to snapping the points on to the output object generated by Fillet or Chamfer, the crash would occur when the output object was removed from the geometry database during the process of creating a new output object for the updated distance.

Most commands do not allow you to snap points on to the output objects, Fillet and Chamfer are the exceptions to this, and they were the only ones that ran into this particular bug.

It's fixed now for the next beta.

It would not be very surprising if there were still a few more glitches like this to get worked out, the on-surface snapping in particular involved quite a lot of changes to the point picker.

- Michael