There's an option to just check constantly, forget how it's described in the settings.*
But I saw users with the same issue....
And they switched from intervals like yours to that, & it actually got much better.
It seems counter-intuitive that it would, but it did for them.

Of course if you want to use the interval, I'd suggest a full reset/re-flash & see if it goes.
I have seen countless folk with weird issues, only to have them disappear after doing so.
Also IIRC, the issue you're describing sounds very similar to at least one logged in the bug-tracker, try searching it.

*don't have my N9 yet...