I have broken more of the flip-lock style than the slide-lock, but that might just be me...
If the flip-lock tab breaks then there's nothing else to do with that connector. But if the slide-lock breaks, you can sometimes push the locking mechanism into place with a toothpick or small screwdriver.
Solder would be enough to hold the connector, if you are gentle with it and don't yank it around too much. After all, that's how the FPC connector on the other end of the cable is attached to its board. You can also add a drop of epoxy or hot melt glue to help secure the connector.
Keep in mind that this board is only a kludging aid. In production boards, there are additional large SMT pads on each end of the connector to hold it down more securely.