Backend 500 Http error after translation update

[Brighteyes]

So I've just updated a translation, clicked save, saw a green tick then the site crashed.

The front end works but the backend shows an HTTP ERROR 500. I've attached what I get in debug mode but I can't make head or tail of it. Does anyone know what might be wrong here?

I've tried deleting the the var/cache/ folder and have also tried different versions of PHP but no luck.

[Brighteyes]

Here's the title to the debug page. The translation I was changing btw was the text that says "List of products by %brand_name%"

[MatteoIommi]

Hello @Brighteyes,
Since there is a mention to ets_seo, have you tried to disable what seems like a seo module? Just add an underscore to the module folder via FTP.
It's not much but at least we could pinpoint the problem and go from there.