It seems like they had a bug where in some cases they discarded the WHOIS information provided and used the billing details instead. Not only did they disclose private information, they endangered a white label contract I was working on.
Bugs are understandable, especially after redesign work, but the biggest problem came afterwards – customer support were useless. First they insisted it was user error and I simply hadn't entered the right details (I'm 100% certain that's not true). Then they claimed that they were unable to update the WHOIS information because they were just a reseller, so they had to forward my support request on. They refused to take responsibility and couldn't get anything done.
At this point they were taking weeks to respond to every message, even after promising a response within 24 hours. I even asked them for a response even if it was just "we asked again and no reply" which they agreed to then ignored. They wouldn't provide contact details for support at their supplier, they wouldn't escalate to anybody who could do anything, their whole attitude was to ignore me as much as they could and (presumably; I have no evidence of this) email their supplier once in a while when I annoyed them enough.
Meanwhile I had no explanation to give to my client, for over a month. We gave up on the domain. Once I stopped chasing, Namecheap never bothered following up. Namecheap could never fix the problem.
Until that point, I had recommended Namecheap many times. Now I warn people away from them. Now I hesitate to recommend any service until I've used their customer support. I still see plenty of glowing recommendations for Namecheap. I wonder how many of them are from people who have never had to use their customer support.
I have used their support two times, but it was an easy transfer request somehow not handled automatically.
Your story is horrible. I wonder if they care to comment.