I had this mentra to remember how not to loose your nerves when working with technical hardware (and software) : "1 - check the cable, 2- check the cable, 3 - check the cable" because so many time "something is wrong" and it's a cable that is or misconnected or misconducting (materialy faulty) ... now I have to add "then check the power supply" ... after spending so many hours checking all (connection and software) with the power supply we tried to drive here for a project in the last and winning check.
And yet, it's often the case too that one or another power supply in your chain is falty or giving strange behaviors...