We're using wp stateless along with shortpixel on our website. When both the plugins are enabled, it causes significant impact on the load times. To dig deeper, we tried analysing this by query monitor and it seems there is an issue with wp stateless plugin and shortpixel(when both of them are enabled together). As per the query monitor, one of the dependency short-pixel.min.js seems missing from shortpixel.

It seems shortpixel have renamed their shortpixel.min.js to short-pixel.min.js and that is causing the issue.