I have had more than my share of failures from eBay, some very cheap, others like a DOA Xantrex Prosine, and later 50A voltage regulator, so I can speak from experience.
A poor rating from you on eBay is like Kryptonite to the sellers. ANY of the problems I have had from China, the sellers refund the $$ and dont ask for the defective pieces back. In return they want 5 star ratings that either way the issue was resolved and you are happy.
AFTER the refund is made, I do give them what they ask for, but I also note in the review that they resolved problems with defective merchandise.
That said, something is clearly wrong with those LED's, likely the ballast resistors are missing, but I have seen that with higher priced units as well. Regulators are nice but they also often generate interference.