[Hopper clocks > piston crashes the game.]

Thanks a lot for the fix! Pistons now work beautifully.

[Hopper clocks > piston crashes the game.]

Empty Forge doesn't cause piston crashes.

It's not consistent but it needs to be investigated more as it makes Minecraft unplayable.

This is one of the cases where it has to be tested with mods loaded. Even though you refuse to test with mods, remember that people will respond about piston crashes in their way soon, massively. I recommend focussing on this asap.

 

I managed to reproduce it with three mods each, which don't touch pistons in any way:

CC Tweaked - Crashes on piston extension

Iron Chests - Crashes on piston retraction

Iron Shulkerboxes - Crashes on piston extension

 

I also tested Roughly Enough Items which on the other hand doesn't cause piston crashes (perhaps for its client sideness).

 

I hope this info will give you a better idea about the issue. Crash logs are pretty much the same all the time.

[Hopper clocks > piston crashes the game.]

To reproduce: Load any mod, place a piston and power it. Unmodded Forge doesn't crash.

Modders refuse to be part of the problem.

[[1.13.2] Crash when moving a tile entity with piston]

I fully support this bug report. Having some mods installed will cause the crash instantly when extending a piston, certain mods will crash Forge after few extends. Forge without mods doesn't crash though.