At least one other person on here had a dark blur in their display. My first VB had this problem. Turns out it was because the little plastic lens / guard had some kind deformations on it. In the pic it looks like a scrape, but in real life, it definitely looks like some kind of heat damage. You can’t feel anything by touch. There were also little droplets under the lens. This display had been to hell and back. I’d learned to solder with it. The fact it still works good means these can take some abuse.
I popped the lense off, and no more blurry lines. So I just didn’t put the lens back. Image looks indistinguishable from the other VBs in my VB portfolio (I have 4). But be warned, the lense was hard to get off with a razor blade – one slip, and you may be in trouble because the small wires inside the display are thinner than a human hair.