Misspelling of common words such as of, to, you're

This is odd.

This only started after I upgraded to Mojave.

Scrivener is putting a red line under words like TO, OF, FOR, YOU’RE. In other words like the word is misspelled. To get around it I’ve right clicked and selected “learn spelling” but it’s odd, especially since they’re such common words.

Is this a Mojave thing?

Yes:

literatureandlatte.com/foru … =2&t=53893

Slàinte mhòr.