Hi MissSara, the other options you might want to try would be to clear the cache in the Home app and for good measure, Google Play Services (avoid at all cost clearing data cache, that's a recipe for disaster), it works like a parking lot's painted lines. It controls a lot of functions in conjunction with the OS to reduce overworking of the operating system. If the suggested update theory is valid that might cure it -- but, I've also received all updates and have had no problem with my 5 groups.
Once the clearing caches are done, I'd totally shut the handheld down instead of a reboot, wait a few minutes, and then restart. You might also wish to retry removing and recreating the groups afterward as well.
