I've had my B9C V.12 (with HD projector) for several years and due to the inability to calibrate the build platform correctly, I could only ever print on one side of the platform.
Even with the ability to print on one half of the platform only, the balance was off and even with the highest calibration value, would not reach the proper value.
I guess I got unlucky with the lamp too because I had to turn the calibration value for it very very high (increasing exposure time). Prints took an extremely long amount of time.
Later, I wanted to try it again. I had purchased 3 vats and a ton of black resin because I had planned to print a lot. Another problem arose:
The middle section of the PDMS (that dips further down than the rest of the PDMS) would come off on each one only after a couple weeks of being soaked in the black resin. This happened for all 3 vats. For the first 2, there was no leak. For the 3rd, all the black resin had leaked out of the vat soaking the table below, luckily not the projector.
I offered it for free to someone who has a ton of FDM printers and fixes them. He wanted a resin printer, but I told him all the problems and he doesn't want to bother trying to repair this one or spending money on a new projector, and new vats that might leak.
If anyone is in the SF Bay Area, and wants this machine, its yours for $500. It'll probably need a new projector, vats, and build platform in order to be any good.