Looking at the picture the first thing I noticed was the blade wasn't square. It looked like the blade wasn't tight when you made the cut. Then I noticed there were no blade guide rollers. If you want to make one-shot scarfing cuts with a bandsaw the blade has to be under control.

: Looking at the table saw scarf jig I imagined the possibilities and
: opted for something kinder and gentler. I'm sure you've seen
: this or perhaps done this but here's my jig for a band saw and I
: claim no credit. I stole it from a guitar making website,
: thinking they need more precision they I would. It's 1:8 or 8:1.
: I dunno, but it is safe, easy, and quick.