I'm printing 2-sided pages and i'm using pre-punched paper.
When printing documents with an odd number of pages, the last page gets reversed, so the 4 hole-punch is in the right side of the paper instead of the left, which is wrong. I tried changing between the 2-sided settings in the driver and had no luck. My suplier has never heard of the problem, but it's happening on all the printers of the same kind.
There was a similar issue, when printing letterhead, simplex worked, but duplex would print on the wrong side of the paper first. That was fixed in firmware, so if your issue is related, an update is the answer.
Upgrade one of the C8045/C8055 models to this version, if it resolves it, do the others too