I have good news for some of you hopefully! My solution!!!!

I had the same problem, mouse would get stuck and freeze and my keyboard would also get stuck and freeze and either skip words or make them like "thissssssss".

However this problem only occurred when programs were accessing the hard drive. For example when I tried searching for a file on my external hard drive, my mouse would freeze and my keyboard would freeze. WhenI plugged in my usb 3.0 to ethernet adapter my computer was almost unusable! Basically any peripheral usb devices that made the hard drive work, would freeze my mouse and keyboard.

Then I ran the dell diagnostic program on their support website for my computer (xps 15, 9570). During the random seek and funnel seek etc I would get the mouse lag and keyboard lag / skipped keys or extra keys. I also tried the intel graphics disable panel refresh and nothing happened. At this point was I basically **bleep**... I updated all drivers and went to bios 1.7.0... I also have windows 10 1809 October update. I also ran malewarebytes. 

I then called Dell tech support and they provided a solution that I was not sure would work. I went into bios setup (F2 on boot), selected performance, went to C-STATE CONTROL and unchecked it. I then restarted my computer and its working flawless now! its been about 8 hours and no problems yet, this is with restarts and stress tests. No problem yet. C-STATE apparently makes the CPU or usb ports sleep to save energy!!! Pretty dumb! So after disabling that I get no mouse lag or keyboard lag with my ethernet adapter and external hard drive! Smooth as can be so far!

I will keep you guys updated!

Thank you,

Pete