@PurpleParrot  I’d recommend contacting Dyson support with your serial number so they can send you information specific to your model (as the controls will vary depending on your specific iteration).

They can guide you through the timer options and resetting the machine, if needed.

@PurpleParrot. Here’s my pennies worth! Only contact Dyson as a last resort. They’d only talk you through the same diagnostics as on their website. 

Assuming you’re using the app, I guess there’s multiple schedules set or someone else has access and set one up that’s conflicting. Search for the ‘Reverting to factory settings’ post on this site. This act alone will remove all other schedules and chuck anyone else off.

If it’s faulting on the remote timer, update the software. 

Only when all this fails, call Dyson. Trust me, it will save you time! 

Alright Ben! Here’s the link mentioned by Sam - Reverting your air treatment machine back to it's factory settings.