What kind of failures can be explained by this fix?
Dry solder joints most likely - you poking around with the multimeter brought them back into contact.  It's likely pins of those through-hole components in the top-left area of the green PCB.  But it probably won't stay working for long.  You should unscrew the big green PCB, flip it over, &amp; re-solder all the through-hole components around that power-supply connector (connector, caps, coil).