A word of warning that may be COMPLETELY irrelevant since if it based on the
mavic 2 drone but ....
in the
mavic 2 there is a tiny lug on the circumference of the inner end of the male half of the actual pivot, this lug acts as two things
1) a rotation stop for the arm when the arm is in the flying position
2) from memory it might also prevents the male half of the pivot sliding out of the female half of the pivot. I cant remember if the external screws in the arm also prevent that but it wouldmake sense if they do.
From various youtube videos and my own crash it seems that this lug is, in a crash, susceptable to being broken off the male half of the pivot. The first symptom I noticed was that the arm would rotate slightly when full throttle was applied such that the motor lifted a bit. I noticed the 'broken surface' on the circumference of the pivot but initially thought it was a sprue break off mark. I can't remember what caused me to realise it was damage but I eventually found the broken of lug stuck in the circumferential groove of the female half of the pivot.
I DO NOT know if there is a similar arrangement in the mavic pro since the mavic pro's arm and female half of the pivot seem to be removed and fitted to the drone as a unit whereas they are fitted separately in the
mavic 2.
BUT I suggest that once you extract the old arm and its pivot from the drone, you dismantle the pivot and see what works as rotation stops.
Why mention this, if you by chance get a second hand arm from the likes of ebay then you would need to check that the pivot works correctly and stops the arm's rotation correctly.
Aswith the start of this post, all this may not be applicable to the mavic pro but ..............