I suspect there is something wrong with the font then, perhaps have a look at the console (app) to see if there are any logs related to the warning and log a bu

I suspect there is something wrong with the font then, perhaps have a look at the console (app) to see if there are any logs related to the warning and log a bug with the fonts creator? For reference IBM Plex (Mono) fonts that I’ve been using since release do not have warnings and work perfectly, however when I re-encoded them to add ligatures it turned out there were errors with the fonts, macOS warned me and I ignored the warnings, then I noticed higher than expected CPU usage from apps where I had enabled the modified fonts incorrectly.