Note, the "Affects Version/s" drop down does not list the Minecraft version on my phone: v.16.50. This bug report is for version v1.16.50.

About a week and a half ago, upgraded my phone from old iPhone SE 1st gen to new iPhone SE 2020. Minecraft application and Worlds installed on new iPhone SE 2020 from 1st gen phone via an iCloud Minecraft application and data image. At outset the migration seemed okay.

In the last couple of days, while mining around Y-axis 11, I saw multiple error messages that flashed by too quickly to capture. Something like object reference not fixed or recorded. Same error message appeared perhaps 6-10 times in quick succession while mining. Then within a couple of minutes after the error messages, player avatar instantaneously "jumped" from mine level Y11 to ground level Y69. Since first "jump", I've rebooted the application and phone. Since reboot, this instantaneous "jump" happened a second time.

I'll try to get a log file next time this happens.