I just experienced a similar issue with a refrigerator and a chest freezer. Both were one of the first appliances discovered by sense, both I physically verified its identification by cycling power and making sure sense detected the changes. I then labeled the devices correctly and added make, model, & locations in my home. Sense monitored them both fine for 2 weeks, and then merged them. I don’t understand why they were merged or how to separate them.
I found this post and reached out to tech support as suggested, who said that deleting the devices is my best option as they cannot be un merged. I asked them how to prevent this from happening again, like a “do not merge” option. They said no option exists and they would notify the data science team, to prevent it from happening again. Do I have any other options on preventing this is from repeating itself?