The MB dealership wouldn't even consider a goodwill repair (54k miles) on my 99 E320 unless the part was defective. They claimed there was no design problem with the H/B, and hadn't repaired one in the last 2 months.
I had my independent put a new one in for $230. He told me that a customer had recently paid $4,000 in repairs due to a malfunction in the H/B. $230 is good insurance and let's you sleep at night. I may even get a refund one day if there's a recall on this part.
Thanks to all who have contributed to this thread. I never would have known until it was too late.