Riding home this evening my chain jumped off the big ring as I powered up a hill. That's unusual; this bike is normally pretty solid on the transmission. Then later, dropping to the middle ring the chain got caught between the big and middle rings meaning I had to stop to disentangle it. That's only happened once before, thinking about it that was the last time I rode it, and in exactly the same spot.
Looking down as I carried on home, the spacing between the rings was varying, looked like a bent ring
Got home, and realised the actual problem was that four out of five of the chainring bolts were very loose
Thinking about it, I last touched them at least a decade ago... at least it was an easy and zero cost fix, and nothing actually got lost on the road.