Please see here for a brief introduction of what I'm about to request.
RetroArch version 1.7.8-1 on Manjaro would not run at all for me. After some research (and finding the above link, amongst other links) I find that it's a package issue.
Therefore (and I apologize if this isn't quite the best place to post this) my request is to push the latest version of RetroArch from the Arch Repos (or however you package RetroArch) into the Manjaro repos. 1.7.8-3 worked for me from Arch's website.
Thanks in advance!