You may recall that a while back, I did a series of reviews on my Sigma brushes, including the F30. I mentioned that the large powder brush worked pretty well, except it shed hairs on my face and bled dark dye during weekly washings.
Well, as I continued to use the brush and wash it weekly, the problems got worse. Now, the bleeding dye didn't bother me as much (since it didn't bleed when dry) as all the little black hairs on my face every time I used powder. I wasn't happy with it at all, but couldn't understand, since I love every other Sigma brush I own. After mentioning it in tweets and on other Sigma lover's videos, it was clear no one else seemed to have the same issue. So, I emailed the company to ask what's up.
After a couple exchanges of emails describing the brush's problem (and some minor confusion about which brush was giving me trouble, which was quickly resolved), Sigma offered to send me a replacement. It arrived a few days later, and I have to say - thank goodness I emailed them! This brush, which looks identical (they even sent it in the same aqua blue color), does not bleed dye and I've yet to have a hair shed on my face. I was worried that I wasn't washing the brush properly and had damaged it, but when Sigma offered to send me a replacement, and then when it arrived and didn't have the same problems as the previous brush, I knew that I had just gotten a lemon. It's rare, but it happens. What impressed me most is that Sigma offered to replace the defective brush, and did so quickly and nicely. It reaffirms my confidence in their products.
So, if you ever get a disappointing product from a company with a great reputation, try contacting them and asking about it. It might be user error, it might be a lemon. Either way, you'll be able to fix the problem. Excellent customer service and consistently quality products are what keeps us loyal.
(Non-affiliate option: www.sigmabeauty.com)