Hello, Chris…… this thread goes back a few years, I contributed on the issue of holding the blade when sharpening, but to answer your questions:
1 – The Blade: Check that there’s no swarf of other stuff in the groove that it sits in. The geometry of this plane is fairly simple, but there was some ‘variation’ in the quality of manufacture over the years that it was produced. (It hasn’t been made since the 60s/70s in the UK.) When the blade’s mounted there should be an EXACTLY equal amount of protrusion below each side of the skates – if not it will stop cutting after a couple of strokes. I’d adjust the blade cross-sharpening angle to this rather than a dead right angle. …. unless it is wildly out of alignment. If that’s the case it’ll need a closer look.
2 – This may be the effect of wavy grain in your wood. It’s best to score both sides to sever the bits before you start and as you go either with a knife or a well sharp mortise gauge. Don’t take shavings that are too thick. and ensure that both the corners of the blade are pin-sharp – as well as the cutting edge. Slightly rounded corners can give a raggy cut or worse, stop it cutting altogether.
3 – The shaving deflector is the one thing that most people never use…….. I never have, however it is intended to sit in and to replace the depth stop that is just in front of the blade mouth. Rotate it so that the angled part aligns with the side of the throat.
The original instruction sheet that came with the tool doesn’t have much info, but it is readily obtainable online as a PDF if you search for it. Also, there are several videos on the plane and its set-up in You-Tube if you search.