Sounds like you need to look at the Transmitter end point adjustments. Are you saying the Sherman, regradless of what transmitter is used is having turret issues?

Try, moving your trim adjustments, and not just the horizontal, try the vertical as well, and see if it gets better. When the window on the BARC4 programming was tightend up to allow more functions, I did notice that I had to be much more precise on the sticks to get the functions to work. One of the issues I was having was this apparent turret traverse problem. An immediate fix was trim adjustments, but I ended going in and programmed the end points.

Same thing could be happening to you.