Bigshew e-mail address
shew@shaw.ca

Possible problems are that the chain, while sharp, may be unevenly sharpened (one side sharper than the other, one side with lower rakers, etc.). Something where one side of the chain is removing more material than the other side. I think it could also be possible that if your rails are unevenly worn (one side flared and/or one side lower than the other) it could also contribute to one side of the chain removing more material than the other.

Simplest test would be to try a new chain on the saw and see if that fixes it. If so, then you could have someone reground the old chain back to even. If the new chain does not fix it, I'd look to the bar. I can't think of anything else.