I always create a Notion weekly plan for the next week every Sunday. I hardly change the content after creation, so I want to activate the "page lock", but the checkboxes seem to be disabled too.
I notice this too the purpose behind the page locks is to avoid accidental edits. A workaround while the page is locked is to open the page in the database and edit the data there even if its just a simple checkbox.
Think of the page lock as a view only (to avoid accidental edits).