I am also having this same issue. Recently purchased a Ring Stick Up Cam with a Ring Solar Panel. Wifi connection is good. It lasts for a day or 2 at a time and then disconnects. When this happens I can fix the issue by getting up on a ladder, take the cam down. I then remove the battery, put it back in and go through the setup procedure to reconnect to the wifi.
One time I was able to fix the issue simply by removing the plug to the solar panel and then reconnecting it. Note that the device appears to have plenty of power (according to the Device Health dislayed in the Ring App it is always above 80%.
I was considering buying a few more cameras, but if this is how they work, I think I may be going with another company for my cameras. I can’t keep taking the camera every few days to re-boot the device.