4K External Monitor Issues

All,
I have read a lot of this forum and it is very helpful. Quickly, here is my situation:
MBP Late 2016 with 16GB RAM, 2.7 i7, 2GM VRAM
Parallels Configured to 4GB RAM, 1 GB VRAM, 3 Processors
External Monitor: Samsung 28" UHD 4K Monitor
Parallels Build 41491 (12.1.1)

When I use parallels on my MBP alone it works great, I have no issues.

As soon as I plug into my 4K monitor I have all kinds of lagging issues. Particularly dragging windows around, scrolling through large spreadsheets, or just scrolling through anything in general. This is a huge problem for me.

I have tried Scaled settings, best for external monitors, and Best for Retina and I still have the issue with the external monitor.

I run OS X Resolution on the external at 2560x1440.

I really need some guidance fixing this issue. Has anybody else had this experience? I imagine it has to be related to graphics cards/drivers specific to this monitor or any 4K monitor?

Thanks everyone.

 

Hi @MichaelS26, please try Actions > Reinstall Parallels Tools and let us know if that works.