New install of Upfront, Posts table growing to 60MB

I noticed my database backups grew at some point today form about 4MB to over 50MB.

Looking at phpMyAdmin I can see lots of unusual entries being entered in the posts_table every time I edit a page in Upfront, see attached image of phpMyAdmin for a couple of simple edits I just did as a test. That table is over 50MB on its own.

For each of those entries that have "rvsn" in the post_status column there is a whole load of random characters, starting something like the following and in all each one is about 177,801 characters long – that's a lot of database. nearly 300 rows on a new install of Luke & Sara them with about 3 three pages/posts from other test.

A tiny sample of the mysterious code:


For each edit I do in Upfront, I get several entries like this in the database, they are huge.

I have turned off all plugins and it's made no difference.

I have run two respected database optimisers, one being "Optimize Database after Deleting Revisions" that can get rid of any old revision data, but neither plugin made a difference.

This is a new WP install and I'm building it up bit by bit on a local DesktopServer environment and up to when this problem started, all has been running well, it still is except for these large db entries which are growing at every tiny edit.

All I know is I had a couple of odd things happen around the time this started, one was I lost some edits when I pressed the backspace key and the browser went back a page (mentioned in another question and probably not related?), and the other thing is that for a while edits weren't showing when I revisited a page in Upfront to re-edit/check. That problem seemed to clear itself after logging out and then in again – both those things happened around that time so I'm thinking maybe something got corrupted but I have no clue what to do now.

Has anyone seen anything like this before or any ideas for a fix?