I suspect the latter (worn out). Wonder if there's a warranty? I have one pole out of two that does that.
I also fell badly on them at the rogaine in SD a few years ago and they both were bent, one pretty badly. JJ straightened it out enough to collapse it down so I could get it home in my luggage but I also wonder if that damaged them a bit.
I'm heading to Alaska this summer and will be doing a bunch of hiking; I may need to invest in a new pair.
These are probably the same ones that went to Kilimanjaro with you? They deserve retirement!