I fixed the issue. The problem here is that the gird (available through Edit -> Settings -> Paint Grid) was not rendered on the whole layout area. More details in commit.
renyiyuan you can download tomorrows (14.06.2021) nightly and test. Of course, thank you for the bug report and welcome in our community!
Screenshot from fixed version:
Klugier
Ah, sorry, I completely forgot about that option. Thanks for the fix!