When you have a Resourse pack that loads only for ingame on specific worlds the game fails to load certain textures and its necesary to close and reopen the world until it loads them.

On the other hand, if you have resourse packs saved when logging into friends worlds the game will constantly load and unload certain textures of the saved resourse packs, (UI textures) even though there is no textures aplied for that world. (playing with vinilla resourse pack)

Ps: No resourse pack is aplied for local game either