I see your post.

There's no such thing as chlorine lock but your CYA is very high. I'd guess as a result of use of tablets. You can run a pool with high CYA, there has been some discussion on this subject here on the forum. Have you read through Ben's Best Guess Chart?

Another note: We don't put much stock in pool store chemistry test - there's alot of reasons but suffice it to say that they are often misleading. We recommend the Taylor K-2006 kit for reliable testing.