Occurred on upgraded 1.10.2 world regardless if direct or stepped to 1.11, 1.12.2. Crash does not occur on 47a or 47b. Shifting floor should harvest flowers and grass after bonemealed in this case. Link to original build: https://www.youtube.com/watch?v=9SpFsltTz74

So I can test this with a hopper clock now which is slower and it doesn't crash. However the grasses and flowers are not popping off.