Panasonic 100-300 CPL issue

My contact at Panasonic has offered to test my 100-300 with my B+W Cpl at the their McAllen Center. But I do not want to give it to them again after what I went through. Panasonic makes a Cpl for that lens and I have suggested they test that one on a 100-300 to see if their own filter does not cause the problem.

My tests on a tripod with remote release shows the lens can not focus at 300mm with a quality (B+W) Cpl on low contrast subjects, but auto focuses just fine without a filter. It's a Panasonic auto focus problem.