S7-391 running WIN 8.1 On startup and for up to an hour after the computer will scroll downward without pressing a key or touching the keypad. Can't tell if this is a hardward or software issue. After a time, it stops and all functions well. Seems to be localized to the UP button which doesn't work initially either. If I hit escape key it stops scrolling, whether in WORD, CROME etc. , but shortly after starts to scroll again. Anyone have any thoughts?