Then it’s definitely permission problems or your ISOs being incompatible/bad.
It can’t be the issue that certain cores work and others don’t and that this is the cause of iOS 5 - either everything works or nothing does.
Perhaps meancoot has some more ideas here but I am pretty confident it has nothing to do whatsoever with RetroArch here and more with your ROM files - the permissions on them - permissions on the ‘folder’ itself - and so on. GBA uses an interpreter CPU core just like every other emu so that can’t be it - DS and PSX use dynarecs but on a jailbroken untethered device that should work.
Either way, you need to provide us with more information in any case - crash logs and whatnot are needed here - because all of this isn’t telling us very much.