I had written in a few weeks ago about a table that wasn't saving changes. Someone kindly fixed it by "Switching recent code from wikitext to html". Well, I now have another table that won't save changes.
It looks like Kirkburn switched it make to wikitext after sending you that reply. So that page isn't using HTML directly either.
Okay, I did a test edit and think I figured out what is happening. Way back in like 2015, somehow you converted the tables to HTML. Since you appear to be using VisualEditor, it is possible that this change was an unintended consequence of a temporary bug with the editor. Regardless, it converted your table from wikitext to HTML. Now, when you try to add rows with VisualEditor, it tries to insert wikitext into the HTML. It does save but the mismatch between languages counfuses the various parsers that interpret what the page should look like. As a result, your edit ends up as separate text above the table. Look just above the table and you will see your attempted edits as plain text. The "quick" fix would be to go through and convert all your tables back to wikitext. However, I would also suggest using this form to inform Wikia staff of this issue. Just tell them that the VisualEditor is not able to properly add rows to tables that have been created using HTML.
Thanks for the update. Although, I was under the impression that VE was a FANDOM-specific feature; so I am not sure how updating MediaWiki would help. I could be entirely wrong though. I don't have much knowledge about the real inner workings.