Tried doing some revising this evening and had a frustrating mystery problem show up.
Revising a single listing. When I finished the changes, ebay would sometimes pop up with

and refused to save. No indication of a problem area.
Tried bulk edit, most items were no problem but some got flagged...

Tried to figure what they had in common (such as bundled or not in the catalog), but no luck finding a common element.
Also ran the eBay bulkchecker on i-ways.net -- all listings are fine for https compliance and active content.
Running a desktop computer so not a mobile app issue...
...
I think I'll take a break and come back to the issue after some sleep (and the hopes this just another eBay temporary problem).
-..-