We have a number of people playing on the same MCPE realm (10 person). We have a large number of devices connecting (ipad, iphone 6, windows 10 PC).

On occasion, after logging in, we have noticed that portions of the world have been reset to the default state. This has been observed at least 3 times in the past two weeks.

In the attached picture, you can see that the forest has respawned and replaced a wall. A portion of the building has been completely reset and a number of blocks in the train have been removed.

The replacement of these map sections looks to have restored the original blocks that were created on initial server spawn and completely removed all player actions (but only in the replaced area).