This is found using the LibreOffice on-line on the tdf nc server. The file in question is here: https://nextcloud.documentfoundation.org/f/76592 this is in the shared work space; Shared->ODFAuthors->English->Calc Guide->6.2->Draft->CG6216-CalcFunctions.odt Track changes is turned on for the file. The last page contains a new heading 'WEBSERVER' and a table. Both added via LOOL today. If I try to edit (past into) a table cell or even change the style to say OOoTableText LOOL throws away the changes and redisplays the document from the very top. It has done numerous times, I even let it sit for while and tried again just now - same result, changes lost and display refreshes back to the top of the document.
Created attachment 145457 [details] propblem file from LOOL I needed to keep working on that file so I made a copy of it, with the content still giving problems at the end of it, and attached it here. I was able to get around the problem on the working copy by downloading it for editing with the desktop application. The link from the earlier comment is the file after those changes.
The darkening and redisplaying means the kit (the core instance that handles the document) crashed, and is reloaded, that's why your changes are getting lost. Confirmed on this server. LOOLWSD 6.1.1 (git hash: 6914108f) LOKit LibreOffice 6.1.3.1 (git hash: 10(Buil)