Hi Mark,
Each caching feature may have different setup or priorities when combining them, especially if they are not considering the proper order of which to combine. Which will then result in CSS not working or faulty javascript.
I myself is not a fan of combining scripts/css as they sometimes not work, and this is not about the recent updates as it also happens on older versions too. Plus, the theme and builder scripts are already optimized and minified, hence, if a plugin minifies it again before combining them then that’s also the problem.
Plus, combining them will only put them in one file and there is no much improvement in it since they are already minified and optimized, or none at all. And in a download speed sense, it’s faster to download a 4 part 5mb files asynchronously than a single 20mb file, still depends on internet limit.
Try disabling the minification on your SG plugin and see if you can still combine them. Though, using CDN is much faster than combining if your site has a hard time serving those files.
Thanks!