When you download the default texture pack from the official minecraft addons page and you change the painting texture and use the texture pack in a realm, sounds like dying and opening chests and doors are very strange. I recognized it and the sounds come from fortnite. The healing and regeneration potions also have another texture based on fortnite. This only happens in realms. When I upload the pack to a normal world everything works fine. Upload it to a realm and you get this.

How to recreate:

1) download the texture pack (https://www.minecraft.net/nl-nl/addons)
2) Change the painting texture
3) Upload the pack to a realm
4) Open chests/doors or look at the potion textures or just drop/pick up an item

Side note: the painting texture doesn't change, it still shows the normal textures!

This is a very strange bug so please fix this. I searched the internet and I found out that I'm not the only one with this strange problem.

Update: I just noticed something. When you go into the realm it asks to download something for 7,3 MB (Not the size of the texture pack). I went to settings > Storage > Cached data and i saw a file named: Miscellaneous (7,3 MB). Other players with the same problem also saw this file. Deleting this cached data doesn't help. When you join without downloading the file the paintings stay normal. When you download it the paintings are still normal but the weird sounds and textures are there.