You know I have been scraping straight edges for 50+ years. I think you could make it better and stop the flip flop I bet your experiencing or good one time and bad the next. I would bet if you laid a precision ground parallel cross ways (width) on the SE you will find it is convex or high in the middle on parts of it. It looks good on the far end, but the section on this side of the vise looks like that.
I know you know this but I'm reaching out to the rookie scraper hands. It is easier to scrape on the side your standing on and it gets low, also if your stone is concave you can do this. I recommend using a small dry stone medium grit Indian stone. small size would be 2" x 2" and not use mineral spirits and wet stone it. I tell the kids to dry stone 5 times and wet stone it 1 time. You just want to remove the burr not increase the percentage. Also measure the low scraped spot. minimum of .0002" and max .001 or average .0005". Also hang it from a hoist and use a dead blow hammer and "ring" it to vibrate stress relieve it. 2 or 3 times during the scraping should work. After picking that up to blue up you will look like Popeye...lol
