If you want to try to fix the custom driver yourself, you're looking for a line (or lines) similar to these:
device.sendEvent([name: 'supportedThermostatFanModes', value:['auto', 'on']])
device.sendEvent([name: 'supportedThermostatFanModes', value:['auto', 'cool', 'heat', 'off']])
Update to:
device.sendEvent([name: 'supportedThermostatFanModes', value: JsonOutput.toJson(['auto', 'on'])])
device.sendEvent([name: 'supportedThermostatModes', value: JsonOutput.toJson(['auto', 'cool', 'heat', 'off'])])
You'll also need to add the import at the top of the driver:
import groovy.json.JsonOutput
I recently had to fix a driver I develop when this issue was uncovered... define supported modes as JSON_OBJECT · dkilgore90/google-sdm-api@76cb524 · GitHub
