This means the problem is likely not related to the recent server move and the changes I started to implement.
The problem is very strange as he only receives some extra notifications and so far I have no idea in what situation this might happen.
In any case I wanted to let all of you know that I am aware of this now and I am trying to fix it. It turns out there were 0 unit-tests checking that part of the code. So the first thing I'll do is to add some unit tests and see if that brings up any edge cases that might explain this behavior.