Hi Daniel. I've just had the same problem for the second time. It can be one of many reason but very unlikely to be poor quality Adblue. It could be the NOX sensor, the injector or as in my case just a poor signal coming from the DEF control module that lives in the boot under the tool kit. I would recommend taking it to a really good diagnostics place so they can get to the bottom of it. In my case they took the controller out, put it back in and the problem went away (albeit probably temporarily). I've attached a copy of the invoice that details what they did and how they tracked it down.
Sales Invoice SJ007643 (1).pdf