Those unmarked cups are the real problem. Half of them have lines that rub off before you even get home, and the ones that do have marks are sometimes printed wrong. A kitchen scale is the only way to go with resin, you weigh both parts and it comes out right every time. The cups they throw in those kits are a trap because they look helpful but they set you up to fail. Two days sticky means it never cured right and there is no fixing it, so you just eat the loss and buy a scale before you try again.

That chatter on the corners is the real tell here, not the rough finish. Stainless work hardens the second your tool rubs instead of cuts, and a cheap uncoated mill dulls faster, which means more rubbing, which means the surface gets harder right where you're cutting. So it's a loop. The tool wears out, the part gets tougher, the next tool wears out even quicker. On stainless that loop bites you way harder than it would on aluminum or mild steel. You can run cheap tooling on stainless if you keep the feed up and never let the tool dwell, but the margin for error is tiny. Keeping a spare of the good ones is cheaper than redoing 15 parts.