I think one of the reasons that some search fund fail is that they get too involve into one particular deal, advance a lot with it and forget to keep the deals pipeline updated, meaning that when the deal they have being focusing on doesn't come through then they basically need to restart.

IMO, the primary reason why traditional searches fail are: 1. Unable to identify a target that meets the narrow investment criteria of professional SF investors, 2. SF investor IRR expectations are above those of many LMM PE firms (who also have committed capital), causing searchers to lose in most competitive sales processes for good companies, 3. Proprietary deals are increasingly becoming more difficult to find due to technology advances which allow a larger number of market participants to reach out to potential targets (databases, email marketing, etc.), 4. searcher realizing that running a small company with the SF model is not the right fit, the searcher economics are not attractive enough, or the opportunity cost of searching is too high. From a searcher perspective, some of these risks can be mitigated by going with a self-funded search.