Take a look on page 18 See item 3 and 6. They work like a rocker. put the blade on and not position and how it moves as the wheel turns, Then loosen the two bolts on one side and tighten them on the other. Does not take much. Then check and repeat. If you take apart to work on or clean etc, It can take a while to get it back into proper alignment.
I have a grizzly horizontal bandsaw that I was ready to throw away because of this problem at one time. I got to reading about tension, and discovered the tension should be very very high. I turn the the tension adjustment wheel until I absolutely cannot turn it any tighter by hand. It’s never come off again while cutting. I’m not saying it’s the same problem, but experimenting with different tensions, and just tightening the bejeezus out of it are a little different. Might be worth a shot.