Hmmm. One of the reasons Lee is an industry standard is due to their consistent quality, also partly why they command a big price. If you are getting colour cast problems like that I can only think that either you got a bad copy, or as they say..."you're doing it wrong!" ;D
As far as Lee, well...they are LEGENDARY for their supply problems. Not just for the Bigstopper, which took off in popularity I'd say a few years ago and made an item already produced in small numbers, incredibly hard to find. I received my copy from Robert White in the UK (link is shown earlier in the thread) about eight months after ordering. And that was because B&H, Adorama, Amazon, every US supplier I Googled didn't have it in stock during that entire time! I'm sure some did, at certain times, but with only 1 or 2 arriving in stock they would be gone instantly, so it would only be sheer luck to find one somewhere.
It has also taken me literally a couple of years to assemble the bits and pieces of filter gear I wanted for my various lens sizes, I have a one stop and a two stop ND, 105mm circular polarizer, Foundation Kit (also notoriously hard to obtain) and the low-profile rings to adapt for 72, 77, and 82mm filter rings. I had to use different suppliers and hunt them down, one by one. I would source one ring from one random supplier in the US, another in the UK - a virtual treasure hunt!
So why all the issues? Lee is a bit of a throwback company, they literally make every filter by hand in England. If you want to see a really interesting video that
may relieve a bit of the frustration of waiting forever for their products to ship, or at least answer a few questions, check out this link:
Mike Browne visits Lee Filters
There is no Cheap Chinese off-shoring here, they are
hand-dipping each filter to dye them and then individually testing each one manually!
And this is expected to supply behemoths like B&H!
Having said that, the effort made the success of getting them all the more sweet, as well as the pleasure of using high-quality, truly handmade products with beautiful results. But if it's instant gratification one wants, better to go with a cheaper (and nearly as good) competitor.