If you are using lightbox on your site, and it is stops working when Swift Performance is active, probably there is a javascript error.

  1. May the javascript error is not even related to Swift Performance. To check it, please disable Swift Performance, open your site, and check, that is any error in Browser Console.
  2. If it seems the problem is related to Swift Performance, first please be sure that jQuery migrate is not disabled. After WordPress 5.6 many themes requires jQuery migrate again to work properly
  3. If jQuery migrate wasn’t the issue, then try to disable Merge Scripts. If it solves the issue, then probably there is a script which is not compatible with Merge Scripts feature. You can disable Merge Scripts, or exclude problematic script from merging