As I move my mouse around the screen it will briefly get stuck at random points then start moving again. This doesn't happen on the MacBook Pro trackpad…only when I have a Magic Mouse connected. This also happens most often on the left 1/4 of the screen when coming from the right side of the screen or trying to transition from the lower to upper half of the screen.
This started happening right after Security Update 2018-002 for Sierra 10.12.6.
Restarting hasn't fixed it.
My cursor size in Accessibility > Display is normal.
Best Answer
I have found that sometimes the surface you're mousing on can have surface qualities that alter the reflectance of the mouse's IR beam and this can affect the cursor behavior. Study the mousing surface to see if any part of the area that maps to the screen has a change in color or texture as this can contribute the the behavior you're observing.
Otherwise, you can try to reset your mouse by unpairing it, removing its batteries (if its an older Magic Mouse) then reseating the batteries & re-pairing again with your computer.