Hi!
I got a CZ SP-01 and last year replaced the trigger with a single action only trigger. I was confused all year as to why it would occasionally stop working... only later realized that I had left everything else stock (without removing the disconnector) and that was most likely the issue.
I switched the trigger to a SA/DA trigger today and found that double action doesn't work unless I first gently pull on the hammer a couple mm before I hear a click, then the double action works.
Have I destroyed something internally with my first attempt? I wasn't able to find any other information on this specific issue.