I was also getting this problem last night. The game slows to the point where it is unplayable.
Note: Both times it happened when I approached my pen full of various animals. We were also playing 3-way split screen. The first time it resolved itself after about 1m. The second time I had to quit the game (which is quite annoying when combined with the bug where other players lose their inventory MCPE-26498)
Perhaps a duplicate of https://bugs.mojang.com/browse/MCPE-26498?
Hey Joseph, do you mean you unplug your internet cable, or just set the game to offline?