Rotating the iPhone while on sign-in (Microsoft Live Login Menu) popup (reproducing MCPE-174398) now guarantees crash some time after rotating.
Steps to reproduce:
With Minecraft Preview open and Microsoft Account signed out, click "Sign in"
With the XBOX sign-in popup open, rotate your device
Expected result: At worst, when the game (app) was rotated, the game still would not crash.
Actual result: game (app) rotates and guarantees a game crash after some time, however the game won't crash until the phone's rotated
Note: This bug can't be reproduced on Apple iPad, and can only be reproduced on Apple iPhone. However for relating bug with pink screen on iOS (and iPadOS), please check MCPE-185373.
For players, The workaround is to turn on rotation lock from control center or settings so the phone won't rotate based of you rotating and cause the game to crash