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Crash protection is a spring-loaded mechanical breakaway device outside the motor housing. If you look at axle coming out of the motor (towards the cassette), there's a silver cam that should still spin as normal when you shift. If it doesn't, the internal gear train is knackered.
You'll see a spring loaded arm that presses on the cam. That's the crash protection mechanism. If it's engaged with the cam then crash protection is not the problem.
grams
iamalex
My 8050 rear derailleur got very upset during its last ride and wouldn't shift out of 34/28 coming over the top of a hill full gas. Motor started making a grinding noise, like nothing inside was engaging properly. Seems like it's now permanently in crash recovery mode - After resetting at the junction and pressing the shifter it makes the tic-tic-tic noise like it's jammed. Motor/cage remain disconnected and I can move by hand. Everything works with a 6870 derailleur swapped in.
Plugging the charger in to the junction and running e-tube recognises the derailleur.
Any top tips before I find a shop with the proper diagnostics box thing or consider it toasted?