In the GBA version of Rayman 3 Hoodlum Havoc, there are four levels that use the GBA's rotation and scaling effects on a background layer. It produces that classic fake flat "3D" look many racers and RPG's of the 16 bit era had (particularly mode7 on SNES).

On mGBA, the floor surfaces in these levels are visually misaligned with the actual track layout. You'll constantly hit invisible obstacles and fly off the track because the graphics don't match the collision. Jumping also causes the floor to jerk and shift violently.

I'll attach several savestates taken at the entrances to the affected levels (press up on the dpad to enter the levels). They're taken from the US version of the game. And here are examples of what the levels are supposed to look like without the glitch-

https://www.youtube.com/watch?v=8SVsl0gjaqc
https://www.youtube.com/watch?v=I_dUSXbUO4o

Rayman 3 Savestates.zip

Incidentally, I haven't tested Rayman Raving Rabbids on mGBA yet but the game shares a lot in common with Rayman 3 GBA (same visuals and gameplay, I suspect the same engine, it's basically Rayman 3 GBA's sequel). It also shares the same kind of "mode7" levels and I wonder if they are also broken..

In case this info is necessary, this issue is present on both the 0.4.1 stable built as well as the 0.5-3929-d8c773b Nightly, both downloaded off the official mGBA site. The glitch is present across all devices i've tested on. My PC has Windows 10 64 bit, an Intel Core i5 4670k and an EVGA 1060. The newest mGBA core running via Retroarch Android also exhibits the same issue.