The way I came across this bug was when changing a large 1 block tall plane of grass blocks. Since there was no light underneath the platform, it would lag when removing the light from underneath the platform when the hole creating the light (from the sky) was filled in. This only happened when the light went away.
For me it specifically caused a 2 - 3 second lag in root.tick.keyboard
Alun Blue
The way I came across this bug was when changing a large 1 block tall plane of grass blocks. Since there was no light underneath the platform, it would lag when removing the light from underneath the platform when the hole creating the light (from the sky) was filled in. This only happened when the light went away.
For me it specifically caused a 2 - 3 second lag in root.tick.keyboard