Topic pane shows blank for a child project

[I have a merged layout (currently 30 projects merged) using RoboHelp 15, MSIE 11, Windows 7 ENT.]  

(I searched to find a discussion about this but didn’t easily find one, my apologies if this a redundant stream.)

The topic pane shows blank for a child project (but, TOC displays correctly).

I think this is due to a mistake where the source folder and the output folder temporarily had different names, and guessing the parent project can’t handle the folder name mismatch.

So, my guess is that publishing the child project temporarily fixes the problem, but the permanent fix is to delete the merged child, then re-merge. I’ll post my results tomorrow, I hope.

Make sense?

Has anyone had the same or similar issue?  Or does something else cause this issue? thnx