No luck with them for me either. I ordered them for a buggy project but used 2 of them in my 11lb truggy. Each of them lasted no longer than 20 runs.
The red arrows shows where the failure started. On the first one 2 gears came apart. And on the second one 2 gears stripped.
Aside of the failure they are a bit slow, seem to be lacking power for Truggys or Mts. Mine also got slower with time and did show the same centering problem.
I would not recommend them in truggys or MTs when used for heavy bashing. When used on a track they might hold up longer. In my buggy they had enough power (still a bit on the slow side) and would have survived longer.
I will now try a Hitec HS-5985MG which features a case top with two brass axial bushing. A Hitec 5955TG might be a better choice though.