Yeah. Decoupling capacitors are for smaller ripples than that. There might be a resonnance point on that regulator, or maybe a maximum capacitance that was vio

Yeah. Decoupling capacitors are for smaller ripples than that. There might be a resonnance point on that regulator, or maybe a maximum capacitance that was violated on the feedback. There are a TON of ways to screw up your PDN on a PCB. It's nominally a master's degree level subject.