I was discussing this same thing on my Scale X in this thread:
I started having this issue in December, but I haven’t seen it in a week and a half now. To be fair, I always have the app open. I will have to try without the app open and see if I get KG again.
No, it should upload readings the next time the app connects to it. If it is not syncing your measurements, consider contacting support:
If they give you any info about the KG issue, let me know.