We have a long-standing issue with large texture packs that we're not fully sure what causes them, although I have theories. You're on Windows, I assume? Could you try this build and see if that improves the situation? Please report back no matter the result if you try it.
https://dl.dolphin-emu.org/prs/c4/3b/pr-9544-dolphin-latest-x64.7z
(from https://github.com/dolphin-emu/dolphin/pull/9544)
https://dl.dolphin-emu.org/prs/c4/3b/pr-9544-dolphin-latest-x64.7z
(from https://github.com/dolphin-emu/dolphin/pull/9544)