Solar panel - Is this normal behaviour?

Hi, I have a Ring Solar Panel attached to my Ring Doorbell 4. It's only been a couple of weeks. Because it's something new, I'm keeping an eye on it. For the first few days, the battery seemed to drop as I'd expect as if it wasn't charging and then after exactly a week, it went back up to 99%. The same thing happened during the second week. I checked the battery level most days and it gradually dropped down to about 90% and then the next day, it was back up to 99%. The device health does always indicate that the solar panel is connected during daytime. My house (and therefore the panel) is east facing and because we're in the winter, we don't get a lot of direct sunlight but there have been some very bright days. The battery has still dropped on those days. Is this normal? Should I expect the battery to drop 10% or so and then top up to 99%? Is this the doorbell being intelligent enough to allow a slight discharge before recharging in order to extend battery life? Thanks.