The real problem is not that Firefox has issues, but that it's a small enough market share now that more and more web services can get away with not bothering to test on it.
Once I became aware of this, I've been trying to be more diligent about thoroughly testing things on Firefox.
I wonder how many other developers are in a similar situation, where Chrome is their default browser and/or their main debugging environment. Part of the problem for me is that I find the Chrome dev tools superior, and that makes it so much easier to just forget about the rest (not that I'm justifying my behavior, btw).
(Also, I think a lot of people discount how good Edge's Dev Tools have gotten. There too my corporate mandated environment is mostly stuck with Windows 7 and an intentionally broken IE 11 due to Oracle and using their terrible software internally.)
Upon googling, I discovered that drop-down menus have been an issue in chrome (even not using vbox). I'm using zurb foundation for the menu js/css, fwiw.
I still use Firefox as default, both for developing and for general web browsing. It and my set of extensions fit my preferences too nicely and have no equivalent in Chrome. I use Chrome at work primarily for Google Hangouts / Meet, the occasional debug session, or just to have another session. (Trying to get into Chrome's Profiles feature too.) At home I just use Chromium from time to time, mostly because my computer is starting to age and I notice the performance difference for certain things.