Another very common location for cracked solder joints is where the power socket is attached to the laptop’s mainboard. CISS’ method can usually pick this up as well.
If you find the loose connection, the fun will be trying to get access to it… they just don’t build stuff to take apart these days. The power port on the lappy is relatively straight forward (if a bit cumbersome), but often the case on a power supply/charger is glued permanently shut.
