I have a schematic with nested hierarchical blocks. In one of the nested blocks I have a hierarchical block that is repeated 15 times. I modified the block and when copy/pasting the blocks, I could get 3 blocks placed, but the 4th would constantly crash KiCad. Duplicating the block had the same results. Going to do some more testing with a new design fresh in 6 and see if I run into the same problem.
The Mac problem report is quite long, but can add it if needed.
Edit 1: Just got a specific error “KiCad Schematic Editor Error: Unhandled exception class:St12length_error what:vector”
Edit 2: Issue created with attached project and screen recording of the problem.