It's a bit complicated, but I don't think resetting preferences ever helped. The export went fine one time after the resetting, but not the first time. When it didn't work, I cancelled the export and selected another publish service. When I went back to the first one again, the export worked, but only one more time. Sometimes the export goes fast, and sometimes it goes very, very slow. Switching between different publish services somehow seems to help a bit, but only for a short time. I have not tried to reset preferences more than once, but maybe I should try again. I have, however, optimized the catalog twice, and made one more back up with integrity test. I have 40 GB free space on my hard disc, but only 4 GB RAM on my 8 year old MB Pro. I know it's a bit scarce, but everything has went fine until the latest LR upgrade. All my images, except the very newest, are stored on an external HD. A couple of weeks ago, this HD almost went out of space, so I made an exact copy on a new and bigger HD, with the same name. LR seemed to accept this without issue. This is the only thing I can think of that may have damaged the catalog. But I don't think this caused the problem, because the export problems also happens when exporting new photos that have only been stored locally.
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