tem62

Thank you for responding. I have found a ‘solution’ of sorts. Probably not a useful one for anyone else that has this problem. However, just in case…

If it was caused by a plug-in, the most likely culprit was either WP-Filebase or the domain-mapping plug-in. Both had been deactivated, and WP-Filebase had been deleted, long before my first attempt to use theme customization. Both left a LOT of garbage behind.

I would discount any currently-installed themes being the cause because several were initially set to twenty-seventeen and, upon failure of the customization, were replaced with copies of twenty-seventeen with just the background graphics changed. I had attempted to make them children of twenty-seventeen but I couldn’t get them to not pick up the background from the parent. That’s probably not related to the underlying issue.

I decided that untangling this on my own was a fat-chance situation. I reviewed my various sites, most of which were in limbo for non-technical reasons, and decided that all but one would be no problem. I decided to just copy/paste out a few things I wanted to keep for the simple sites and to risk exporting/importing the one extensive site and just blew away my ancient, pre-4.x-origin installation and reinstalled with a fresh 4.9.8.

It is so nice to be able to use the customization feature now. Now that I am comfortable that my WordPress installation is once again stable, I may spend a little more time on some of those previously-shelved projects.

Thank you again for responding. Since I can no longer test against that installation I am marking this as resolved.