Guys, I think I found the reason why the uniforms are not showing up. The "cop_presets_outfits.xml" file provided by RDE is a few bytes in size and contains 1 outfit. A "preset" outfit with the variation name "agent". If someone else more experienced wants to take a look, I've uploaded the xml file.
cop_presets_outfits.xml
In the callouts "Impaired driver" and "intoxicated person", the suspect is completely sober after being tested with a drug swab test and a breathalyzer. Also, the dispatcher skips the name of the call when saying "we have a...", resulting in "we have a, in Vinewood hills." Callouts "Assault", "Person with a firearm", and "Road rage in progress" do not activate, even when forced using the callouts menu. On the "Police impersonator" callout, after arresting the suspect, a notification pops up saying "you found a gun when searching the suspect", however, manually searching the suspect does not reveal any weapons. Upon accepting the "Domestic" callout, dispatch immediately says "code 4 - disregard".
In the "Strip club gang attack" callout, when I call backup units, they begin shooting at me, the player. They cease fire when dispatch says "code 4", so it is likely connected to the callout itself.