Have you tried disabling Bluetooth access on the Dyson, and then re-enabling it? As a further step (if needed and if available) you could try a complete reset of the Dyson to factory defaults and starting from scratch.
In my experience it is usually the 'other' gadget (not the phone) that is causing issues because the phone continually gets updated and the gadget lags behind, or doesn't adress technical issues that crop up quickly enough.