Just yesterday our long-running MCPE started crashing when opening a world. Sometimes it crashes while displaying "Syncing with server", sometimes while "loading terrain", sometimes within the first 2 seconds of actually seeing the world. This only happens when the wifi is on, though. With wifi off, it loads fine.
We updated our iOS to 10.3.2; MCPE is v1.1.2. Both are fully updated as of this posting.