Not unusual these days quality of builds, soldering on PCBs, cabling, etc
poor.
I use a magnifying glass and inspect PCB for solder joints missing solder, ones with
partial solder, cracks......
Also power related components that need heatsinks, look around them for burn marks
where a component is getting hot. If thats the case not unusual several components in-
volved in the problem.
Any screw terminals loose where wire connections being made....
Regards, Dana.