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Main lessons learned:
-Start testing out possible solutions immediately, and document what changes.
-Always check your assumptions (I forgot the multimeter leads had resistance at one point)
-Make sure that you know your board like the back of your hand, then you know where all the extra pieces for testing need to be put (I had to get creative with some of the components placement)
-Make sure you’re using the right tools for the job - a clamp meter trying to measure inrush current on a 1ms timescale will not do anything when your inrush current only lasts for 8ms. Know your measurements timescales and the limitations of the equipment!
-Sometimes seemingly complicated problems can be caused by simple effects → inrush current and ESR causing voltage droop = reset loop