A tale of 3 Skyvipers : Another motor and gear issue

My first 2450GPS , the wife bought for me at Christmas from Costco here in Canada . Worked and flew great from the get go. It did suffer from two hard crashes early in its life , due to dumb me hitting the power button and disarming it in mid air . This resulted in a broken right front arm , was able to repair with glue and tape , but turns out this motor was also damaged as it would some times not spin after arming . Replaced that motor and once again drone flew great until around end of May . It seemed to lack power and developed bad shake in video , I assumed that rest of the motors were now worn to point that they would need to be replaced . The Wife not looking forward to having to help my trembling hands solder a joint on those tiny wires again , ordered an other Skyviper from Amazon reseller, Sweet! It arrived in short order , paperwork said it was used / open for testing . This one was also the Costco version with extra battery and included SD card :smile: I noticed right away that this Viper was very noisy , gear chatering and super twitchy flight and bad jello video. Close inspection reveled that rotating the props with my fingers that one prop would hit a rough spot and stop , turns out the pinion on that motor was missing 3 or 4 teeth . Easy fix to replace with a pinion from Viper #1 Noisy chatter went away but video was still quite jello’y. Checking free spin by hand that prop still catches a bit . I thought perhaps the teeth on 73 tooth main gear could also be damaged .I swapped it out with one from Viper # 1 as well . Checking free spin by hand it still has a rough spot were it seems to bind . I’m lost as to what is causing this is it a bad motor ?
In the mean time vendor had emailed Wife asking for feed back on order,she told them about issue with pinion they immediately offered to ship another complete SkyViper Awsome thank you Amazon :blush: , which is due arrive tomorrow so that will be Viper # 3 .
Anyone have any thoughts on what is wrong with gears .
Also what size and type are the little jst/molex plugs on motor wires are ?

I think it might be these

Sky Viper motor wire plug (=connector on flight controller) is Micro JST SH 1.0mm.


Thanks for the help folks .