Firstly, I apologize as I don't have any footage of any sorts regarding this matter, but in my Minecraft world, there is a specific chunk, particularly a village, where the mobs and items seemingly move in slow motion while the rest of the game runs with relatively smooth 120 FPS. When mining blocks, there is a huge delay before the items spawn from the mined block, mobs move in jittery ways, and the sounds are delayed when doors are opened. 

As far as I know, this does not seem to happen in other parts of this world, only in that specific chunk. I have heard of tick speeds, but I have not messed with the tick speeds in any way for this to happen for that specific chunk. For what it's worth, though, I put the simulation distance to the max settings that's allowed by default by the game.

EDIT: Here is the affected world, it should spawn you right at the village where the bug occurs. Hopefully you are able to reproduce it.

My World.mcworld