Has anyone had their case transferred to another office and then heard absolutely nothing for weeks or months afterward, without any explanation or update, and if so did it eventually move forward normally or did the transfer cause additional delays?

Yes, that happens to a lot of people and it’s usually just part of how USCIS shifts workload around. When a case gets transferred, it often sits quietly in the new office’s queue until an officer picks it up, so the silence can last weeks or even months without any updates. In most cases it does eventually move forward normally, and while the transfer can add some waiting time, it doesn’t usually mean the case is delayed because of a problem.