Closed Singleplayer "server lag"

When playing in singleplayer, every few minutes I experience what feels like a server lag spike (though, being singleplayer, this is obviously not the case).

When this occurs, the following is experienced:

• Monsters/NPCs all freeze in place (even if mid-jump or mid-attack).
• All interactive objects become non-interactives (doors won't open/close, chests are inaccessible, etc.) - attempts to interact have no effect until the freeze ends (at which point, everything happens simultaneously). This includes digging through terrain, harvesting plants/crops/trees, and other such interactions.
  
• Any attacks made on frozen monsters/NPCs silently "stack," their total damage being applied on unfreeze in a single burst (striking a monster 3 times with a sword does 3x sword damage on unfreeze).

As an added bonus, when I'm hosting a server and playing with other people over a network, this lag doesn't occur - which eliminates my computer lacking adequate resources, as this scenario obviously uses MORE resources, but doesn't lag.

This bug has been ongoing since a few updates back, starting after some sort of major change in the game engine that (I think) set things up so the game is running some sort of internal server or something. I'm not really sure about what's going on except that it's managed to get me killed a few times in various ways.