Base Layer objects no longer visible behind New Layers

Thanks, Alyssa. Thought of that too.
The eye icon is on (unlocked). (And I played with it, to no change, in the troublesome file.)

Did a little more exploring on this this morning and can give these additional notes.

I actually opened other older files and found them working like I expected, then went back to the file in which I had been working, only to find the troublesome results again, from any page. I opened a new file to start a new build and found its pages to be working correctly, so started one by one to import items, starting with the template pages, checking layer workability after each step. (This included imports of pages from the Serenity template and then adding pages from the Opportunity template. All pages' Add Layer tests worked fine after each step.) 

I then started importing pages from the troublesome file a scene at a time. As far as I can narrow it down to, the troublesomeness arrived again when I imported the multiple choice quiz pages, which are using the Opportunity template as a layout, but were modified to use the Serenity 02 feedback styles. One good variant in this newer file started this morning, the problem (at least for now) seems to be only happening on those quiz pages. (I get an opaque layer if I ask for a new layer on those pages, but I get the normally translucent layers when asking for new layers on any of the other pages. That is at least better than I was getting in the original troublesome file, which made any new layer opaque on any page. And since I really don't add many additional layers to the quiz pages, this new combination is at least not nearly as meddlesome to my other non-quiz page slide builds, where I do extensively use the layers.)

The troublesome unexpected response seems to be relegated to something within this file. (Though, as my initial post stated, this is not the first time I've seen this in the last few weeks, so I am going to go back and see if other files where it occurred also used the Serenity 02 feedback pages, as that is an item I started using more recently as one of the departments I serve started using that style as a standard.)  I Sorry I cannot send files so you could see the difference, but our corporate firewalls prevent any file sends outside the system. (It also blocks my interaction with the reply button for these discussions, which is why I have to keep replying as a new entry.) At least I get to keep seeing and reading input. 

Will try to see if I can get it narrowed down to a culprit in the files or templates, but at least am now reassured the program is still working the way I expect it to. And I always appreciate the back up of colleagues.

Ron