So you dont want to improve the forums by leading by example, you just want to be an advocate for not helping. Seems you either:
A: Dont really have a solution and are just looking for attention
B: Have and answer. but dont really care about the forums either, so your excuse is actually hypocritical.
If I were a betting man, I suspect its A.
For others. Im on 5.5 atm and have found the most consistent success Ive had (when I see this problem)
- Download Texture Source (I usually do 2K)
- Create Joints Only Rig - this is necessary for the Assemble.
- Run the Assemble - I select UE Optimized and choose Medium Level.
Then.. if things went well. I often save and restart. This seems to resolve any preview / render issues.
Hope that helps.. now.. if I can get the default clothes working.. thatd be nice.