Mobile submenus not working on most pages

I'm having an issue where the main submenus are not opening on many (but not all) mobile pages. I don't seem to get this issue when I'm logged in and test my site in mobile view in Firefox. But if I try using my phone or mobile view in chrome or open an incognito firefox tab, the submenus break.

Caching is the most likely culprit. I use W3 total cache, Cloudflare, and have memcache and Varnish on my Cloudways server. I've tried turning off JS/CSS/HTML minify in W3 (most likely causes), turning off the plugin entirely, purging Cloudflare cache, and purging the cache on Cloudways. But the issues seem to persist.

Only other problematic plugins I can think of are ShortPixel Image Optimizer and Wordfence.