My vehicle survived re-entry, so this question is more out of curiosity than for practical help.
I had a ~2t re-entry slug barreling through mid-atmo, heat shield first. I was not getting any overheat warnings, but was suddenly surprised by the graphic and sound of an explosion. Afterward, though, my whole vehicle seemed intact so I continued on. When I landed I could find nothing missing - shield, science, parachute, or otherwise. What exploded? Is this an issue I should attend to on further missions?