Rear drive tanks are very prone to throwing tracks. Things you can do to improve the the situation , increase the tension on the springs in the corners (the rear wheels on either side most inportantly) by clocking them. Make sure your tracks are properly tensioned. Bobs advice is good, misaligned wheels are your enemies.

if your tanks a front drive some idler tension adjusters will help, if your tracks are too loose they become more prone to skipping.