JoomSEF seems to be causing all kinds of unexpected problems with Joomla 3.8.0. I upgraded JoomSEF to the latest paid-for version, 4.7.0, but this hasn't helped.
For example I get a "network error" when trying to export URLs. Also, pages are being displayed without SSL, even though JoomSEF is set up to enforce SSL.
I would like to purge the URLs and have them regenerate, but I daren't because I can't backup the existing URLs.