For quite a number of months this year, something strange has happened to my SP4's type cover. When I'm carrying it around mobile, the trackpad works steadily. But when I return to my desk, where I have a bluetooth Sculpt Comfort mouse to use, the trackpad sensor goes rather haywire and sends the mouse pointer wobbling all over the screen; can't get any precision movement. I've been operating this computer since 2016 and never encountered this problem before - both trackpad and mouse used to work (properly) side by side. I'm clueless what type of interference the trackpad is getting when on my desk. Anybody experienced something similar before?