My Nest keeps adding temperatures to the schedule after I’ve set it. It seems someone else can access my Nest
Keep in mind Nest is a learning thermostat, so it can(will) adjust itself automatically according to your usage. You can disable this by following instructions linked:https://support.google.com/googlenest/answer/9209007?hl=en
Do you have the Learning Nest? If so, turn off 'Auto Schedule' in the settings.
Google Nest Help Center
Chromecast Help Center