Wrist Temperature Not Working & multiple iPhone & Watch Sources in Health App Settings

My wrist temperature monitoring stopped working after several years normal operation. I tried a few things, eventually hard resetting my Watch Ultra, setting it up from scratch & waiting a week for the temperature data to accumulate - still no good. Looking on my iPhone (16 Pro Max) in Settings-Health-Sources I see my current Apple Watch + 8 other "Apple Watch" entries all showing "No data found". I also see 40 (yes forty!) "iPhone" sources in addition to the expected entry for my previous iPhone (12 Pro Max). All the spurious iPhone entries show "No data found" & no option to delete. Something wierd's going on. How can I get wrist temperature tracking working again (& maybe clean up the incorrect health data sources)? - I'd really rather not have to hard reset my phone.