Textures turn bright pink after a long playing session.

Hi, after a long playing session (3 Hours) i noticed that textures started turning pink.
First skins then entities until the whole game was pink

I investigated this issue and it only occurs when a server is using a texture pack.
List of things that turn pink:
Fonts
Crosshair
Top sky part
Some inventory items
Entities / Models
Icons
Skins
and propably more that i didn´t notice

Here are a few attachments:
(I could just upload it here but file size limit)
Pink textures: https://streamable.com/1mfd1m
Normal textures: https://streamable.com/jno1gr