Hi George-
This might be a better question for the Use Any Font support forum, but a couple of possibilities jumped out to me.
When I downloaded Manrope I noticed that it included a different set of web fonts in the __MACOSX directory. You may want to consider using those versions of the font along with a user-agent CSS selector.
I also found a couple other users reporting the same issue, and the font developers recommended using self-hosted versions of the font, which you are, but it’s the version that the Use Any Font API has converted.
That leads me to wonder if the way that Use Any Font does its conversions is causing the same issue as the other users using the Google Fonts version. That’s why I think it might be worth reaching out to Use Any Font to see if they’ve got more information about the issue.
I’m sorry I couldn’t find a definitive answer for you, please let us know if there’s anything else we can do to help.