Had an intermittent fault on an old Lenovo laptop which prevented it from booting up properly. The remedy, prescribed by YouTube, was to remove the battery pack AND the CMOS battery for 20 mins until all residual power had ebbed from the circuits, reassemble and away it would go.
Ah the days when removing the battery was simply pull back a couple of clips and to get to the innards undo a few screws. Now you need a combination crowbar, tin opener and acetylene torch and in all liklihood something will crack as you pry...