Apple Watch won't connect to Polar H10

I have an iPhone 11 (iOS 13.5.1), an Apple Watch Series 2 (Watch OS 6.2.6), and a Polar H10 (Firmware 3.0.56). I use the H10 with my watch when I run (I use the native Workout app). I use the Outdoor Run activity, and I have Power Save Mode turned OFF. When everything is working like it should, I can put on the watch and the H10, start an outdoor run, and the H10 will automatically connect. (I know it's connected because the green leds for the watch’s internal HRM will NOT come on, but I will have an HR reading on the watch.) But every two or three runs, the H10 will fail to connect to my watch automatically. (I can tell because the green leds for the internal HRM will come on even though I am wearing the H10.) When it won't connect automatically, it's often pretty difficult to get it to connect at all. When I go into the Bluetooth menu to see what’s happening, my H10 will show up two or three times under “health devices,” as if there's two or more of the same H10 nearby. Usually none of them will connect and stay connected. I can sometimes fix this by turning Bluetooth off and back on, but sometimes that won’t even work. I’ll have to make my watch “forget” my H10, then pair it with the watch again. I’ve been having this problem off and on since I bought the H10 over two years ago. The battery in the H10 is full. The H10 is also paired to my phone through the Polar Beat app, though I have only used it with my phone two or three times. I have allowed the H10 to connect to multiple BT devices through the settings in the Polar Beat app, so it shouldn't have a problem connecting to both my phone and watch at the same time. I’ve seen others have connection problems with their Apple Watch and H10. Has anyone found a solution?