Test driverversion 17.3.3. all newer cause shuttering in the 3xx series... mainly on dx9 games!
Do you mean rollback the driver?
Yes, clean rollback to 17.3.3.
I test it with my "Asus R9 390x Strix" and i go the driver in reverse.
The 17.3.3. Version was the first one where i have no shuttering and fps drops in Games where i don't have it normaly.
Later version like the newese 17.5.1. do something wonky with the OC function of my card. I get higher frames when the card is at peak .
But when the Card and Software must decide to toggle down there start the problem. I reduce this problems with vsync.. but.. i get framedrops
in older games, mainly dx9 games. Since i roll back to 17.3.3. it works fine.
But the Problem with the driver after 17.3.3. is not only limited on games. I have Problems with Win10 and the Software "Display Fusion".
When i deinstall it.. it reduce the problems but they are there. If i grap some desktop icons and pull them from monitor 1 to 2, you get some
minimal shuttering. 17.3.3. no problem.
I think, there are some problems with windows 10 and the OC featuers of some cards. So roll back and hope that AMD fix it in the next version.