For some reason, piston head dissapears when it moves. After animation stops and it becomes blocks, everything is visible again

Hi, thanks for the report.
Can you try switching to a more recent version of forge?
I recommend 28.2.0, and 28.1.56 in case you are using Optifine

It worked, sorry for interruption)
Installed forge 1.14.4 28.2.0 and found another strange thing: this setup creates water particles on retraction for about 1 frame, despite the fact that there is no water near... Is it should be like this? Sorry if it's my second stupid question)

This issue has been addressed in 0.2.2a. Thanks for the report and feel free to re-open if need be.