I've just had my road bike at service because of bad shifts respectively noisy gears on small-big ratios (my lowest gears). Of course I tried to adjust it myself first but never got to an acceptable result, either bad shifts on some cogs or noise, indicating something's off here that couldn't be fixed with just a bit more (or less) tension.
See original topic Shimano 105 R5800 - Noise on largest cog?
I thought I got it because everything was fine on a short test ride and on the stand but the next longer ride proved me wrong.
The mechanic quickly found out that my mech hanger was slightly bent (inwards) and got it fixed without any cost and waiting time, which is great. I'm not aware of any impacts or crashes, just a bit of ambitious riding/racing since the last service and the issue just came by itself, from my memory even during a longer ride.
He said that might be related to out-of-the-saddle efforts that could put stress on the rear derailleur (or the hanger as designed weak point).
I'm of course aware that you shouldn't do hard shifts under load and generally back off power when shifting, especially uphill, but I never heard that just out-of-the-saddle riding would contribute to hanger stress (at least that's how I understood it).
Also, I never had any bad hanger damage with this bike, but could it be that the original hanger that came with the bike is weakened after couple of years and replacement on the next service might help?