I'm creating a new thread since this has NOTHING to do with My Fitness Pal. I've never even tried MFP let alone connected it with Garmin.
For me, as an example, I did a scale reading last Saturday and uploaded the scale reading data with body metrics just fine. On Sunday I get a false weight reading and at that point the Saturday body metrics are wiped out. This has been going on for months for me and looks like over a year now for some. Somehow Garmin Connect or Garmin Mobile is creating extra FALSE weight readings with no metrics and somehow it also wipes out the real reading with metrics.
Garmin has to know this is going on. I know 4 people having the exact same problem. They don't use MFP at all but all body metric readings are erased on Garmin Connect. In the past week I weighed myself on Saturday with metrics and since then I have a weight reading everyday in Connect (even though I haven't weighed myself since Saturday) all ALL the readings have lost the body metric data.
Come on Garmin...fix the problem!