This bug has occurred in 2 of my mid-game Survival worlds (before the Ender Dragon or Wither were defeated, if that matters). Both times it started after my first few trips to the Nether. On the overworld it seems fine, but once you enter the Nether one of two things will happen:

1. HUD shows up, but chunks are visibly missing and some sides of blocks are transparent, and no blocks can be interacted with and Nether portals stop working. When you try to open the pause menu, the loading symbol shown in the screenshot shows up and the HUD disappears.
2. No HUD shows up and the blocks and chunks go transparent in the same way, while the loading symbol in the screenshot shows up.

I am playing on and Xbox One S Bluetooth controller on an iPad Pro 2018 12.9", so when I try to touch the screen instead, the normal HUD for touch appears, but the pause menu and chat are unresponsive.

Each time I restart the world I go immediately back to the Nether to check, and if it is still broken I restart the game and try again, at which point it loads back in at the most recent auto save point and I go back through the Nether. This issue DOES NOT resolve itself after restart of both the game and my iPad, and when I had this issue the first time I copied all of my worlds into a separate folder, did a clean install of the game, and it was still happening on the copied world in the clean install. I decided to try another world (this screenshot) and it too started showing this bug after entering the nether just 3 times.

This is interesting, because I have not seen any other mention of this in the searches I have done, which is good that it is rare, but as a mildly hardcore player that is just getting back into the game for the duration of the COVID-19 outbreak, I find it very disruptive to have literally no access to reliable Nether travel to all of my off-site farms.

If anyone else is having this issue, or if this is bigger than I thought, please let me know so we can try to get this fixed quickly. Thanks for any help.