Steps to reproduce inside the editor:
1) Place block 13-1-5-1-3
2) Place block 5-10-3-1 two blocks above the previous block
3) Place block 13-2-1-1-1 between the two blocks
This will cause the game to freeze. Tested on 2 different machines, here's a clip of it happening live: https://clips.twitch.tv/ReliableGiftedOxPipeHype-XueerXPXJYvTCldR
This is deterministic.
Update: it seems that 5-10-3-1 is not the only block that causes freezes. In fact, there seem to be a common denominator. Any blocks that, when placed in ghost mode, show a curved platform as the second block option (on the left), while they have a square shape, will cause a freeze. For example, 11-1-4-2-2 has a square base but when placed in ghost mode, shows a circular alternate block on the left.