Printed the card scanner files and my scans keep coming out blurry on one side

That washed-out edge on foils is almost always the LED angle, but not becasue the strip sits off-center. Foils are mirror-like, so light hitting them at a low angle bounces straight back into the camera on one side and reflects away on the other. Center of the card gets hit from a steeper angle and looks fine, the near edge turns into a hot glare blob and the far edge goes dim. It reads as 'soft and washed out' because the glare is blowing out the exposure in that zone. Before reprinting anything, try moving the card away from the LED side by a few millimeters if your channel allows it, or put a strip of matte white paper as a diffuser between the LEDs and the card. That alone fixed it on mine. Also check your PETG shell walls, since PETG lets a bit of light through and can add a faint haze on one side if the strip is close to the wall. A layer of black paint or even electrical tape on the inside of that wall helps.

On the bowed card thing, I've had decent luck leaving them in a penny sleeve under a couple of heavy books overnight, which flattens most of the gentle curl without any pressure on the card face itself. The ones that still rock after that are usally curled from storage near heat, and those barely respond to weight anyway. I just scan those tilted slightly toward the camera and accept a softer far edge rather than forcing them flat in the channel, since pressing a stiff old foil down hard is how corners get creased. Curious wether anyone's tried warming the cards gently first, like on a windowsill, or if that risks worsening the curl.

Not buying the paper diffuser fix from the earlier reply. I tried exactly that on my foil scans and it just makes everything dimmer, so the camera or software bumps the gain to compensate and the glare streak comes right back, only now with more noise around it. A diffuser spreads the light out but it doesn't change the angle, and angle is the whole problem with a mirror finish. What actualy worked for me was shooting two passes with the card rotated 180 degrees and blending the good halves. Slower but the foils come out clean.

Not much to add on the lighting side since I'm still figuring that out myself, but on the bowed cards, my situation is a bit diferent. I don't have a scanner shell yet, I just lay cards on a piece of glass over a dark cloth and shoot from above with the light off to one side. What I've found with the ones that rock is that flipping the card over and taking a second shot works okay, then I keep whichever half of each image looks sharp. Crude, but it saved me from flattening a card I was nervous about. Does the ScryScanner software let you combine two passes like that, or is it one shot only?

I'm still at the stage of propping my camera on a stack of books, but I noticed something similar when I tested a shiny card. If I let the camera pick its own brightness it made the shiny part look way worse, but when I locked the brightness at what the dull part of the card needed, the glare calmed down alot. Does this scanner setup let you turn off the auto brightness thing on the camera, or is it stuck picking that by itself?