Custom Spells look "glitchy" and act strange on mGBA

Questions
1

I was playing this old personal rom hack I had made a few years ago and I noticed that whenever I used a custom spell, this weird jumble of graphics, something like missigno for comparison, would show up on top of the screen and I don’t know why.

The other issues I have faced are that the Donbettyr animation has random flickering on the screen and Glacies plays very slowly.

The spells for reference: FE-Repo/Spells n Skills/7. Spells/1. Anima/[Ice] Donbettyr {Alusq}/Spell.gif at main · Klokinator/FE-Repo · GitHub

Thing is, these issues only happen mGBA, in John GBA Lite they play like normal. Is it something wrong that I did back then or is there a setting on mGBA that fixes that issue? I googled and tweaked its settings and nothing fixed it.

2

I learned that is an issue of the emulator, apparently it emulates even the lag that would happen in a real GBA, the only solution seens to be using another emulator, yay…

Edit: Tested it on VBA-M, worked like a charm.