Your comments

It works!

Thank you very much!

Here is the last lines of the log:

[Wed Jun 10 12:07:44.149351 2020] [php7:error] [pid 745] [client] PHP Fatal error: Uncaught --> Smarty: unable to write file /var/www/html/system/data/temp/smarty/wrt5ee0cd102418b3_46688151 <-- \n thrown in /var/www/html/system/classes/smarty/libs/sysplugins/smarty_internal_runtime_writefile.php on line 49, referer: https://XxXxXxX/ - - [10/Jun/2020:12:07:44 +0000] "POST /?module=share&_popup_id=folderShare HTTP/1.1" 500 295 "XxXxXxX" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36 OPR/68.0.3618.125"

I have FileRun under Docker.

Thank you.

This option only appears in the admin user interface. Normal user doesn't have this option. Right?

Yes, I know, but, manually?

When you made the mistake of move files out of interface, what are the steps to set FileRun "OK", I mean, DB, index, thumbnails... What command-line tools and in what order.

Or I have to go to fresh install?

I have FileRun on docker. System, db, and HTML in SSD, and files in HDD.

And I browse folders with hundreds of images very fast.

Would be appreciable the speed increase in this cases changing to an SSD?

Sorry,  I know that it's not about FileRun issue, I only ask for suggestions.

Thank you.

thats seems a permissions problem. 

It is under docker?

With a file explorer that supports WebDAV connections. It's not an app that can upload files automatically, for example.

I had a similar issue, but with other WebDAV client, and I solved it with the @Home.