Just like lots of others using multiple monitors with Winds 10, I have been greatly irritated by the way that the mouse pointer tends to "stick" at the monitor edges when you move it between monitors, unless you are moving the mouse fairly fast (when it transitions from one monitor to another without any issues). Do a search such as this one to see some of the history.
There are solutions involving editing Windows registry settings (or using an app called NSM – Non Sticky Mouse to do the editing for you). I tried these suggestions, to no avail, and the mouse pointer still kept sticking at the edge of the monitor.
I had almost given up when, fortunately, I saw a comment by one person recommending that you go to Display Settings and jiggle the rectangles representing the monitors as close together as possible:
There may still seem to be a gap between monitors, but the action of moving the edges of the rectangles so that they slightly overlap seems to have the desired effect.
A reminder that you may have to log off and sign in again (or restart Windows) before this remedy takes effect.
As mentioned, this seems to work -- but we all know that Windows can be rather quirky (and Microsoft keeps tinkering with these things, so a fix like this may stop working at some pint in time). Only time will tell.