Servo centre point keeps changing

[TheBinarySheep]

I'm experiencing some steering issues since I replaced a cheap 120a ESC with a SkyRC Toro 120 ECU, I don't know if the ESC is the problem or whether it's a coincidence.

I noticed the problem when I turned everything on and the centre point of the servo had the wheels pointing all the way to the left. I thought it was odd, so I removed the steering arm from the servo and connected back on with the servo in it's central position. All worked fine for 5 minutes or so when next time the same happened, but this time the centre point had the steering pointing all the way to the left, again, I fixed the issue but it just keeps happening for no reason at all. At one point I thought it was fixed, picked the buggy up and as I did I saw the wheels point all the way to the left again, all on their own with no input, and it's stuck like that.

I've placed marks on the servo to confirm that the steering arm isn't slipping, and it's not, it's the actual servo. The servo isn't that old and is an Alturn metal gear servo that I've not had any issues with until now.

My radio gear is a cheap FlySky FS-GT3B, which again could also be a cause of the problem, but I'm not sure since I've had no issues with it previously.

If I turn the ESC on, without having the transmitter on, then the steering points all the way to the right, but doesn't straighten up when you turn the transmitter on, so it's like the centre position on the servo ends up being whatever it defaults to when the power is switched on.

Has anyone had a similar problem? any ideas? Could it simply be that the FlySky radio gear isn't compatible with the SkyRC ESC?