I agree with Brian, on this matter.
The first order of business in any business is communication and therefore if you fail to communicate with the customer you will have a disgruntled customer.
I too deal with Molds but in the plastics industry (poloymers mostly) but also some rubber, presswood, and even some fiberglass mold.
we do about 2 mil a yr. with 17 employees and i can assure you that the owner can always be reached on any working day. In our case the customer do not always hear what they would like to hear, but again we do communicate.
With that said i saw for more complaints about like of communication than the quality of your products. I did see one Vega front end that i would consider not useable. By your own statement you say you are fixing some molds. Maybe the quality issues come from those molds that you are now fixing.
I saw where there were 50 something emails and no returns. You said about 10% unhappy, i would think this is unacceptable in any business, 1 to 2% maybe, we don't have that many, in fact if it's wrong we absolutely correct the problem and move on. 99% of our buisness is repeat work, unlike your's 1 customer 1 job.
But as Brain says good news travels fast and bad news travels faster.
I think that you can correct the problems over time but i would definately start with communications either good or bad news. Atleast the customer will know where he/she stands on the money that have already spent, because the ball is in your park at this point.
JMO
Zip.