I do agree that there needs to be some more room for sources to correct wrongs when they happen. I see a lot of posts about 1-2 strikes your out, when some things are beyond their control.
This is by no means an excuse for UG labs, because I also believe they need to behave better when problems do arise, rather than deflect, or get an attitude as I've seen so many of them do.
I personally want more sources to chose from, of a high quality.
To answer your last question, I do believe it is the UGL's responsibility to know what compounds they are mixing, and to accurately dose them. Maybe they can't do every batch because of TA, but they can randomize it, and when a consumer posts problems, they should immediately test that batch and close all lines down bought from that supplier until they can verify contents. Sometimes I feel like they are greedy fucks when they continue to sell despite 2-3 problems being publicly reported of a serious nature.