This thread must come up about once a month! Drip some super glue in the joint. Keep the joint moving as it dries, don't let the joint set. The end.
I use clear nail polish. A coat of that usually does the trick. Just be careful you don't over-apply it and make the joint too tight, and allow plenty of time to dry. I normally put it on what needs doing in the morning and then leave it until the evening to put it back together. Excessive, an hour or two is probably enough.