WRECKS

I am experiencing chatter when the blade moves from left to right. This only occurs on straight line "horizontal" cuts. It works fine in all other directions. Right to left is ok as well. The result is a cut that looks like a perferation. This is the case with various brands of vinyl. I have tried a new blade and adjusting down force. I have very little time on this machine, so parts should not be worn out. Any help would be appreciated. Thanks.