Builds that have worked since 1.12.2 (And not 0 tick farms.) Suddenly decide to lock up the game clients.

In 1.12.2 you would see the moving Redstone flying machines stuttering but the Game would still be responsive:

https://www.youtube.com/watch?v=dftxbF8U8U4

& 

https://www.youtube.com/watch?v=b6aK0BfuGp8

These now put the game in a free cursor [Not Responding] state during the flying machines transition, the game starts responding after about 1 minute for the doors, but the silo build seems to just crash the game out, too long a non response I guess.

This happens in both single player and with a local server (which is happily ticking away as the game client locks up, not only has it done it to myself but to a friend connected externally too.

This seriously sucks for Redstoners.

I would be happy to upload the world to a realm for dev testing and give co-ordinates of the problem builds, but I don't yet have a realm account.