Problems I encountered:

1. Wrench player has to be built from exactly the same WR revision as the recorder, otherwise bad things happen
2. When replaying, all of the keyboard input, title frame number, and actually displayed frame - appear to update at different moments (de-synchronized). It's difficult to fast-forward in a predictable manner.
3. Saving frames when running with --play doesn't get some of the last frames saved.
4. Showing individually saved frames doesn't always get the same rendering as the binary replay.