[Polaris395]

I've used Mecs except 2009.

I would also look and see whether each axle is in alignment with the other ones in a TRI-dimensional environment. Remember that Mecs run on the idea of vectors and so when these vectors are off, the stress on the wheels will increase greatly. I also point out that if you are testing the rubber rollers (plastic less so) on carpet, the frictional force applied to the out-of-line wheels is exponential.

Also, try doing some stress-tests and full power cycles on your battery (don't hurt yourselves!). Batteries aren't built for a strenuous 4 weeks and then mild-no work for the other 48 weeks. (Ahh chemistry.)

If you use Mecs and you can't go to a machine shop, I highly recommend using the supplied chassis with little to no personal drilling. Vectors are fickle!