SpaceX is really struggling with Starship propulsion. Re-entry is a pretty big challenge considering the heat and forces involved. Having it self-destruct on a test pad suggests deeper problems. My dad was on the engineering team for Titan/Gemini in the 1960s and they lost a lot of them during testing.
During a successful launch a thousand things have to go right, and failure requires only one thing to go wrong. Maybe time to bring back Tom Mueller for consultation and analysis. He was the principal designer on both Merlin and Raptor engines that put SpaceX into orbit.
https://en.m.wikipedia.org/wiki/List_of_Titan_launches