SpaceX @sh.itjust.works threelonmusketeers @sh.itjust.works 2mo ago CSI Starbase POGO: The 63-Year-Old Problem Threatening Starship's Success (96 minutes)
Lengthy video, but worth the watch, as Zack Golden's analyses usually are.
Wish there was a tl;dr
Resonance. Old problem, new rocket.