what servo for a mini rio?

[gjxj]

Somebody gave me an old mini rio with a bad servo (I think). It works for less than a minute before the steering quits ( so you can just run around in circles ).

Its very frustrating I can not reproduce the issue out of the water. On the work bench i can operate the servo all day, even putting a good load on it with my finger.
(I'm pretty sure its not getting wet when run in water tho..)

Anyway at this point I thought to just drop in a new one. Any recommendation? or other thoughts on why it has this gremlin?

[gjxj]

here's a couple that seem like they fit size wise.

Hitec HS-82MG
Hitec HS-81
Traxxas VXL Micro Servo