We are experiencing odd behavior with the left navigation, so much so that many of our devs have turned off the new design.
I like the new design, but I have to shift refresh to see the left nav. Otherwise, it either doesn't show, or it shows in a preload placeholder design. This happens when I search or navigate away from a ticket.... basically any time the page has a refresh (maybe it's just trying to refresh parts of the page, as in a SPA, instead of full page refresh, but not sure).
Using Chrome Version 63.0.3239.84 (Official Build) (64-bit)
