I had the same problem with mine, but found it is possible to adjust the track tension.

Be careful and patient doing this, and you should have good results. Remove the tracks, upper hull & turret and make a vertical mark in the rubber mount holds the drive assembly in the lower hull (this both a guide, and is to let you you go back to the factory position easily). If you remove the drive assembly and rotate the rubber mount you'll see that it operates like a cam, and rotating it to different positions will move the assembly forward or back slightly. Move them both the same direction (using the mark you made as a guide) and with a bit of trial and error you should be able to set the tension perfectly.

As far as what the "correct" tension is, I'm not exactly sure. If I hold mine horizontally in the air there is about 1/8" between the track and the center roadwheels, and they seem to run just fine there.

Hope this helps.