I have a scree with 10 sections and quite a bit of buttons, fields, grids, action sets, etc in each section. Last week I was doing some housekeeping and went to reorganize the sections and the page reloaded and only the first two sections were visable. After some troubleshooting I realized the sections were still there, just hidden within the html (display:none vs display:inline-table; see below image). Also, when navigating to the view of the screen, the sections where visable and all functionality apeared to work as expected. The only odd thing is that each scetion's title was changed to what I am assuming is a default section title placeholder, ie: section1, section2, etc.
At the time, I thought there may be something odd going on with the tabs functionality (the hidden sections were in tabs). The two that were visible were not. I changed the setting - Advanced Screen Properties > Section Layout from 'Show in Tabs ( Tabs start at section 3 )' to 'Show In Sections' - and that did not solve the problem.
I contacted two of your 'Community Support Specialist' and they directed me to this forum.
Also note, there were no errors in the JS console.
I have more screenshots and can direct a method tech to the appropriate screen, but would rather not post that infomration in a semi-public forum.