Since upgrading from 4.9.x to 5.1.x, the module and page settings have been updated. Whenever I go to “Page Settings” or Module Settings, the new eyecandy on the page page takes forever to load because it is rendering all the icons in the permissions section (see below). The icons come up 2 or 3 at a time every second or so and all of them collectively take about 18 seconds to load, give or take.

I couldn't find anything on the forum with a couple of quick searches.

I was raised thread (the same problem): DNN 5.1.2 - UserController.GetUsers(PortalId,True,True) generate to much calls to DB.

It's look  like UserController generate to much calls to DB.

I can't understand why  each calls to dbo.aspnet_Membership_GetUserByName   generate ~20 calls to dbo.GetUserCountByPortal @PortalId=0
 (return UserCountByPortal)