XRAY - Model racing cars

The active diff is new to me, and this is the problem I am having.

When I use the active diff, car seems to handle well, however after things get warm some binding occurs. It is much the same as if a bearing were going out, however I have checked all in the drive train, and even replaced them although they all looked and felt good. Things are binding up enough that my motor is over heating. I thought I had a tuning problem at first, however after feeling 'stumped' in that arena I found that the front end was binding up under the appropriate load. It is very inconsistent, however noticeable by simply 'dragging' the front end. I have checked the shims (using 1 shim to open mesh) and everything seems actually ideal (ever so slight play). When the car cools, seems as if no binding is present. I will have to check my notes, however I believe I am running Losi, 5k-5k-3k (front to back).

I must admit, I am feeling a little disgruntled. With the difficulty of assembling this thing, (and immediately reassembling to replace bearings) and now the difficulties in running it, I feel that the $114 something that I spent was maybe wasted. Am I missing something? If so, please enlighten me.

Thanks.

With further inspection, I have noticed that there is a bout .100" movement (100 thousandths) in the front cvd forward/backward direction. This allows the gear mesh on the front diff to fluctuate from approx .050" to .100". Is this normal and acceptable?

Maybe it just needs another shim. Mine needs two .2mm shims on the crown gear side to have good mesh, so a total of .4mm.
With no shims it skips when braking.

I got some 14x16mm shims so I don't have to open the diffs to shim them differently when I put them in my different cars.