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