Its picture nests a second w:drawing, and the importer's subtree
search found *that* one's wp:inline first: the box was read as the
bare picture, so every word of the caption in it was dropped —
which is what Word's own Insert Caption writes for a floating
picture. The root is now the drawing's direct child. The export
side gains the caption's SEQ field inside a box, so the running
number stays live there too. Leg 30 covers both.