Topic sums it up pretty well. I've installed 2.8.5 (2.8.4 did this as well for me actually). I don't have any functional JS on the admin side.
Old install was (or is, I reverted) 2.7.1 with all JS working just fine.
As I don't have much experience with WP, I'm not sure what information you need. Just hoping someone here can help.