While cutting the 4x4 square tubing for my power hammer build, I got the blade square to the  tube, but the up-down cut was off by at least 1/16".  It's not a big deal when cutting thin stock, but that's a lot of steel go grind off on thicker stock if you need it to be square.  I thought the issue of the blade's plan of travel not being perpendicular to the surface of the vice area was because of a casting or milling errors.

While changing my bandsaw blade, I noticed these mounting screws that attach the backside of the bandsaw assembly itself to the spring loaded arm that is attached to the frame.  I inserted a couple of thick washers (ground into a U-shape so I could just slip them in).  It's now cutting close to perfect on both axis.

And I've had this bandsaw for at least a decade. 

Thanks for posting that.  I have one of those machines and have had difficulty getting long square cuts at times.  Of course you can get a blade sharper on one side than the other or the guide bearings out of adjustment, but it's good to know there may be another relatively easy thing to correct.