Strange behaviour on GTX 960

I have an issue with my MSI GTX960 Gaming 2G where after a day or so the maximum clock speed of the GPU is lower than previous.
This may sound normal however usually after a fresh boot the GPU boosts to 1366mhz and doesn't go over 60c.
A day later it may go to 1100mhz.
If i leave it without doing anything it will only go as high as 800mhz after several days.
Rebooting sends it back to its maximum.
Also, if i load afterburner and set the
Power Limit (%) to as low as it will go and apply, then click the reset
button to default it, it goes back to its usual 1366mhz.

This issue has persisted through multiple motherboards (the first X99A SLI
Plus I had that I had replaced at the store for different reasons also had this issue).

Running the latest drivers from nVidia with the same issue. I've also tried another PSU.

I can't remember if the GPU exhibited this issue on the old MSI
P55-GD85/i7-860 system I used this card on...I never really checked

But it gets to the point where if I don't keep an eye on it after a week it really affects the performance in game, after a day it's lost 200mhz clock speed which definitely has an impact too.

Any ideas anybody?
Thanks :)

Well maybe this

Otherwise exchange if still under warranty?

Hmm nope not like the issue I've had (0 driver crashes)

And MSI's RMA system in the UK is absolutely dire, usually takes ~1 month to get a refurbed card back (if they do anything at all)...sigh :|

If you've already reinstalled windows and it didn't work you might as well go for the RMA, or just return it and get a 380, it'd be faster anyways