We are exeperiencing some problems with current version of apex with navigation flickering.
The top menu navigation bar flickers when it has child menu items during page load because the icon span is added by Javascript instead of being part of the menu template:
And the same occurs with the sidebar menu if you set it to be allways expanded by default:

It happens the very first time in incognito mode on first login, until you press the menu icon for collapsing and exanding it again. After that it stops flickering on page load. It happens every time the cache and session are lost or when navigating between applications. Local storage options for the sidebar state are not set up until you click the menu icon for the very first time.
Does anybody experienced those issues? Any solution to this? I don't see substitution variables for adding css classes for avoiding this until the apex team fixes this.