Hello! I have come across this problem few times now where the page editor freezes up and the text or any content, not even page sections can not be(picture below) edited/removed.

Blue line shows those three wider/lighter section frames that differs from the normal page section frame on the bottom below. Broken sections can not be deleted manually nor using ''delete section''- tool on the page editor tool bar.
Tried to fix the problem as follows:
1. System upgrade AND weekly program restart - Not working
2. Co-editing app restart/on -> Off - did not help
3. Copying the page with the full content - section blocks still non editable
What causes this problem, and how to fix this??
Maria A