I am also having this same problem with menu switching with specific files (two files, one a copy of the other), but not all files I've created with Publisher. With those files, the only way I can get Publisher to go back to its original menus is to quit and restart the program. I did the defaults reset and opened one of the problem files. Publisher started off with its own menus, but I checked about four or five minutes in, and the menus had switched to Affinity Photo-like menus. I have other files that this does not happen to. At least, not yet.
The only things in the problem files were text, rectangles drawn in Publisher and an imported EPS logo. I've used the same logo in other files that don't show this behavior.
To answer the questions, yes, I have Affinity Photo installed, but it was not running when I worked with Publisher.
I did not insert any Affinity Photo files. I did not insert any raster images at all. I did insert an EPS file, but I used that same file in other test documents without a problem.
I can understand the frustration. I've tried to duplicate the issue with new files and not been able to, but this issue is consistent every time I work with those problem files.
I am using Mac OS High Sierra on a 2017 iMac.
Additional: I posted before I read new comments about the text styles menu. I'm seeing that, too.
