Apple Health App Keeps Repeating Weight from an Unknown Source

I've searched here and the Internet and have not seen anything like this. Haven't reported it to Apple yet; thought I'd try here first.

I use an older Withings WiFi scale connected to their Health Mate app to record weight weekly. It is the ONLY source given permission to write weight to Apple Health. It correctly syncs to Apple Health within 30-60 seconds and the Health Mate icon appears next to the data record in Apple Health. But within one or two days, Apple Health will start adding the exact same reading over and over to the weight data, with an iPhone icon next to it. I have verified many times that NO OTHER app has permission to write weight data. And if one did, I would expect the icon to be specific to that app, not an iPhone icon. I even suspected maybe the weight I manually enter into the Medical ID of Apple Health may be writing it back. But I always round the weight to whole numbers when updating the weight in my Medical ID and the mystery weights always appear with the same full decimal values as the original weight from the Health Mate app. I do not have any other iPhones activated and only have one Apple Watch connected (Series 4) that has no weight apps of any kind.

The solution so far has been to manually deleted the errant data once a week, sometimes as many as 20 data points, to keep the chart trend lines accurate, as I am on a very serious weight loss journey and as a diabetic need very accurate info for myself and my doctor.

Anyone have any clues? Thanks in advance.