I need some help with my Hitec system.

I have a TC3 Electric RTR. It came with the Hitec radio and servo system consisting of the Lynx Sport AM 27MHz radio, HAS-2MB receiver, and the HS-322HD Deluxe servo. I bought this June 24th this year.

My problem has existed since I got the car. I believe I've narrowed it down to my servo. When my batteries are fresh, I set the steering trim and make the car drive straight. However, it either goes straight when I accelerate, or when I coast. I can't adjust it to go straight all the time. Then, as the batteries start discharging, the car starts pulling further and further left, and I have to keep adjusting my trim to the right. By the time my batteries are near dump my trim is nearly all the way to the right. I've adjusted my steering countless times and have had it checked by more experienced racers, it's good. I've heard through the grapevine that this is a symptom Hitec has been running into, so I'm hoping you can help me.

Thank you!