Workaround
Seemed that closing and reopening the project resolves this issue
This is NOT a regression as it happens in 4.15.2
Result: There is a second instance of the asset selection option UI flickering
Expected Result: There is no flickering or second option UI
Frequency
6/10
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-44388 in the post.