I've noticed this on my board, and now I just experienced it on this board as well. 

I just received a Push notification (Chrome browser) "Your topic was solved!". Clicking it loads the following "Sorry — Page not found" page (the preview here looks correct but if you click the topic title or the arrow icon you'll see what I mean). 

 

By comparison, clicking the same notification in my notification pop-up menu on this site loads the correct page:

 

Thank you for bringing this issue to our attention! I can confirm this should be further reviewed and I have logged an internal bug report for our development team to investigate and address as necessary, in a future maintenance release.

 

Great, thanks a lot Marc!

This issue has been resolved in 4.7.0 which has recently been released. Please upgrade to that version to resolve this, and of course, let us know if you are still seeing any issues.