In single player worlds, occasionally while breaking blocks, there will be a big lag spike. Then the player and block states revert to their state a few seconds prior. Similar to what I have experienced on servers before, but as I said this is in singleplayer.

I have tried to find a common thing that may be causing this, but as of yet I haven't noticed anything. I have only noticed this in the past couple weeks. Previous to 1.14.4 release I didn't experience it.