Syncinc Apple Health data

Hello,

I have a strange problem with Apple Health which is unrelated to the device. I did not find a topic that really fits the problem but it probably has something to do with the local Apple health data on my device.

I have an Apple Watch 2 and the health data from the watch hasn't synced with my iPhone for half a year. It started with taking longer and longer to sync the data to the phone, sometimes about a week, until it stoped to sync the health data completly. Everything else like pushes and calendar data were still syncing but not the health data. Because I was working on my master thesis I had no time to deal with this problem but now I have spend some time to find out what is wrong.

At first I just reseted the watch but it didn't solve the problem. After that I did a full backup of my iPhone and restored my iPhone with that backup but that also didn't work. Then I reset all the settings on the iPhone without any result. It finally worked when I did a factory reset but without restoring the iPhone from the backup. My conclusions so far: The watch does work but something unrelated to the iOs settings causes the watch to not work with my iPhone.

Then I restored an old iPhone with the above backup and were using that iPhone for a day and interestingly the watch would again not sync the health data with the old iPhone. So the problem does also not have anything to do with my iPhone as a device.

Currently the watch is connected to the old factory-reseted iPhone. Everything is working beside the fact that it is no long term solution to use my new iPhone but connect the Watch to my old iPhone. The health data are synced with iCloud without problems. But then I discorvered a new dimension of the problem: The new iPhone where I did just a reset of the settings and no factory reset has also problems to load the health data from iCloud. At first I thouhgt that the data doesn't sync at all but after two days the data was suddenly synced but did not sync again until now. This problem is similar to the problem above that the health data from the watch didn't sync properly.

So a conclusion to this weird problem: The health data on my iPhone doesn't sync properly even if I backup the iPhone and restore it on another device or if I reset all my iOs settings. A factory reset does fix the problem but I don't want to lose all my data from about 10 years.

Thank you already for reading that long text and for any upcoming answers!