Servo's not returning to center
 

I just bought two new servos to replace 2 that failed. I got a Spektrum S6250 High Torque HV Dig Servo inside my cc-01 Wrangler chassis from Tamiya. And I have a Savox SW-1210SG waterproof coreless steel gear digital servo inside my son's Exceed RC off road buggy 1/10th 2.4Ghz Brushless PRO 2.4Ghz Electric SunFire RTR Off Road Buggy (EE Green) RC Remote Control Buggy.

Both of them are not returning to center after releasing the controller. The Savox is horribly off. Even after mechanically centering the servo. It pretty much returns to full lock right turn. The Wrangler will be about ~8 degrees off whatever direction you just turned. So if I'm driving right and then try to go straight, it will return to almost right, and turn slightly right.

Another note on the Savox, I've noticed it doesn't really turn every time, either. Like it has to think about it or something. I've contacted both manufacturers with no response.

Exceed is running an unknown model number ESC. It worked fine with previous servo, but came with the RC and the manufacturer hasn't given me the model number yet to know. The Wrangler is running a Futaba r203gf. Again, no issues with either ESC till the old servo's went and new ones were installed.

Anyone have some input on how to fix? I'm still a bit new to all of this.