I’m in too deep with the MP3432 now 
But I probably wouldn’t be able to hear the noise once it’s in an enclosure.
About the power-off flash, I’m looking at whether I need to hack in a potential divider to set the MP3432 UVLO higher.
You have oscilloscope and cant find whats ringing? So how we suppose to know?
You just gave me an idea, I’ve only been scoping the output voltage which looks fine to me. I should really also scope the MP3432 SW pin to see if that’s oscillating. Wouldn’t really help with finding the root cause, but could still be something.
Yes you have to scope every single component .
Quick update: Using the MP3432 UVLO fixed the power-off flash.
Can you show the full schematic ? (Can be in MP if you prefer)
Sure, the plan is the release the full schematics after I’ve ironed out the problems. I’ll PM you the current set.
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Another quick update: With guidance from @thefreeman, I recalculated the three resistor values to the MP3432’s FB pin, which has further reduced the noise.
I’m making a ultra detailed video on this circuit, and will make a fresh write up when everything’s ready.
Thank you to everybody who helped!
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