update version 2.4.26678 on Mac Ventura 13.3.1. running Safari.
Tried all the usual; switching settings, turning off, sacrificing chickens etc. but it still doesn't work.
Sent you a feedback email as well, as nothing seems to get done with the bug reports on here.
Same here using the desktop version. It's inconsistent highlighting "...ise." and "centre" in particular. Damned annoying for a Brit.
It's a major issue with an unknown "resolve" time. I have found if you run the Consistency report, it will list all spelling errors both for British and American English.
It's not a foolproof solution but a good work-around until PWA fix whatever they broke.