Need help with slow loading slider in Firefox & Safari

I have a couple of sliders on my homepage that are loading lightning fast in Chrome on Windows, but takes about 10secs to load in Firefox as well as Safari on a Mac.

We tried analying the waterfall data in browser console to determine what may be causing the sluggishness in only these browsers, but haven’t found anything conclusive.

We’ve also checked with the Query Monitor plugin, but it reports as is well with no issues.

The site is running through CloudFlare with SG Optimizer plugin for cache. We’d tried flushing that as well with no change.