The DMX Operator(pre 192) has a "Delete all" function, which is a good idea to use if you just got it. better than fighting with unknowns as you program through it. Clean slate is always the best way to go.
Chases rely on scenes. MIDI implementation requires scenes. Chases can be deleted, banks of scenes can be deleted and the whole thing can be deleted.
A chase is a sequence of scenes of your choosing, running in order based on a trigger(audio input, typically a bass note) unless using a timed setting.
My suggestion: blow out the whole thing and start fresh, as you're suggesting. It's in the manual, so if you can, download it and check it out. Now make your own scenes and then your own chases.
Have fun!