Symptoms

A CSS error was getting caught by the developer tools when trying to load certain forms at runtime.

SCRIPT5009: 'Sys' is undefined

This was heavily degrading the rendering of forms.
 

Diagnoses

n/a
 

Resolution

Check the following keys to see if they have been disabled.

<add key="UseBundledFiles" value="false" />
<add key="Forms.PostRenderCombining.Enabled" value="false" />

Changing both of these to true in conjunction to giving Domain Users full control to the runtime folder resolved the rendering issues.