There are cases Glyphs applies wrong sharp/smooth connection type to the nodes when:
- Drawing with pen tool (happens a lot when you click-click-drag-drag. The first click in the sequence of clicks gets marked (mistakenly) as sharp, and first of the dragged nodes become sharp.
- Connecting nodes, certainly the nodes that are the ends of curved segments. If you cannot see it, try reversing the contour.
- Deleting nodes. When you, say, delete a crossbar of H from Times which has a bracket serif, the end of the bracket segments become sharp for no reason.
Also related to confused node positions, when you select a curved segment (all four nodes including off-curves) and option-delete it, the second node of the open path is somehow selected. Could you get this thing off?