The thumbnails in the reference viewer are broken and do not reflect the thumbnails in the content browser.
This is a Regression from 4.14.3
Spoke with BenZ about his change to the Asset Registry, but this was not effected by that.
Result: The thumbnails are broken and do not reflect the asset
Expected Result: The thumbnails in the reference viewer reflects the thumbnails in the content browser
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-44111 in the post.