Resetting the Syncthing index

I use Syncthing1 to keep my laptop, desktop, and workshop computers in sync.2 At least 99.9% of the time it works perfectly. Rarely, it seems to choke because of some edge case that I’ve never been able to sort out. But it never recovers on its own. Instead, it continues to report that a remote is 99% done syncing. The workaround that I’ve learned is to simply reset the index.