I fixed my problem by running msiexec in quiet mode in an /32Bit winbatch.
wmic uninstall still doesn't work in winbatch /RunElevated but the msiexec /X procedure works too, so that's my workaround.
I don't know why it's stopped working after all this time but after pulling my hair so hard i'm glad it's solved.
Thanks Scrooge for you time.