I made a report about this and can confirm that a bell was part of an issue. I was in a desert biome by a village. I hit a bell while in split screen and then I destroyed it to move it as the well needed to be cleaned up. I ran over to my friend and the whole map lagged out like the description says. My original ticket was MCPE-46842 if you want to go back and check out any details. Let me know if you need any other proof or tips that could help.
Same actually. I just created a separate and detailed bug report based off of the same issues but more intense. I could not find this report though so I feel bad when I am found out! I am trying to uninstall the Beta program. I will let you know if it works. It is so annoying though!
Update: After a few days, I was able to get the same exact map that was freezing to work again after just starting. It worked all day and to the next day until that evening it randomly froze and did the same thing. The second time, I was in split screen and was in a village with an unaltered bell. I logged easily 5+ hours if not 10 before it crashed.