Possible drop-tables case

Recently I had this really annoyng bug with Polylang. It didn’t occur in my local dev environment (WordPress 4.4, Polylang 1.7.12, WAMP 2.5 default settings), but occured in production server (WP 4.4, php 5.5.30, 5.5.45-cll-lve – MySQL).

Anyway, here’s the thing.

Biographical info in edit user.
Inserted text in english, containing phrase something like blah having blah.
Updated user.
Updated user again.

Now, after second update’s page refresh- page not found (404) returned.
From this point, you can use browser backbutton, refresh profile page and everything shows nicley, but there’s no chance to fix this really, because new value never gets saved, instead you get 404.

The solution to overcome that issue, is just manually delete this user biographical info from database. After that, user profile update is possible again, until blah having also blah text is entered and all previously described reoccures again.
So, to narrow the scope, I disabled Polylang plugin, and inserted same text to biographical info textarea. Updated user, updated again and updated third time to be sure. Everything worked like it should, no 404.

Since I’m not professional backend developer and I don’t feel myself too comfortable with database operations, my guess is that the culprit here is related with SQL HAVING clause and/or input string escaping in plugin.
I tried to add wordpress built-in and PHP input sanitation functions to Polylang plugins admin-filters.php, where seemingly this bio (description_ $lang) field gets saved, but still had no luck to get it work with this phrase properly.

I hope this issue gets attention by plugins authors.

https://ww.wp.xz.cn/plugins/polylang/