Today we had a very rough day, one of us had created a WCF REST service, and other one was trying to consume it in his IOS application, but he was not getting the correct response. We tested that call using Fiddler, could not find any problem in that. We tried very hard to troubleshoot why was that happening, but no luck.
We enabled WCF trace and message logging, although we could not log the actual message body, but we were able to review the headers of both calls. We found several differences other than the user-agent, and we experimented with most of them.