P2815Q, Mouse Lag issue

Got this monitor couple of months ago and it's driving me crazy.  I used to have a 27" Dell display that worked perfectly but got this new one for the 4K and it being 28".  Since then I've been fighting my mouse. It's clearly a lag from me moving the mouse till I see the action on the screen. I work with AutoCAD so I tend to move the mouse a lot making the mouse lag that much more of a problem for me. I had no clue that this was a 30Mhz screen or anything other than it's a Dell monitor and up till now all my Dell monitors have worked flawlessly.  This one on the other hand it driving me crazy. When I got it there weren't too many reviews but lately I've seen more and more posts from people complaining about the mouse lag and not getting any answers. I've tried all the ports with no changes and I've tried different mice without any luck. It's starting to look to me like a MAJOR flaw in production of this monitor model and Dell should be able to see that on the numbers of people complaining about this ONE ISSUE.