Actually I have a Mac M3 - and I too can see this exact problem.
More info: I'm pretty sure I didn't see it till my recent upgrade to Tahoe AND it only happens only on my external monitor - built in display is fine.
Monitor DELL SE2722H - current res settings: 1920x1080
Let me know if you have any other questions (I'm a developer myself and know how frustrating it is when you can't reproduce a bug)
P.S. I really love your app - I've tried a number of different journaling apps, and wasn't satisfied with any of them. Since I switch to Diarium - I'm stuck for life