Resharper ‘updating source files’ does not stop (in Visual Studio 2015)

when I open up a project in Visual Studio (2015 in this case) a little progress 'thing' pops up at the lower right hand corner of Visual Studio.

AFAIK it is Resharper updating all the assemblies for its intellisense.
Normally it stops after a few seconds, or sometimes 20 seconds on large projects.

Now on this solution, suddenly, from this day, it won't stop!

So it starts small from the right site, grows to the left, then does it again, and again…. (longest time I've waited was 30 minutes).

In that time, the pc is slow and R# does not work in VS.

Already restarted VS and the pc, but that didn't help.

It only is for 1 solution, not for the other ones. And when i double click on it (which I did not know I could do before) it shows, very short, a little window what file it is working on and it shows a filename

(angular.js) which isn't even in this solution (to be complete, it is in another solution, but that is in a separate directory outside this solution.).

I realy don't have a clue….

EDIT

I've found this line in my visual studio .suo file for this solution:
C:\cv\Dev\Dev.2.1\Frontend\js\angular\directives\userAccessDirective.js
(the file is partly binary, so I can't just delete it I guess)
So I deleted the suo file, VS recreated it…. with the same filename!
(and the userAccessDirective.js uses the 'angular' term, I don't know if it has something to do with it, but it's weird that this reference is in the suo file for this solution)

EDIT 2

Removed the filename from the suo file, didn't make a difference