Mine also discharges. I don't know by how much, but 6% per week is probably within the "normal" range.

On the subject of discharge, I can say that mine also discharges about 3-4% per week. However, the manufacturer also writes (I don't remember where, but I definitely read it) that the "shelf life" of the product is three months, so this is probably "normal" and a certain self-discharge with LiPos anyway. The meaningless values are probably a bug. Check whether the values still "jump" even with constant (no cloud cover or shading) charging via solar. The Yeti needs about a minute until the values are calculated correctly and if the charge (which is typical with solar) changes constantly, this can lead to estimation errors.

I have 2 1000s, both hold a constant charge for weeks.
Are you sure you haven't plugged anything in (chargers draw current even when NOT in use) and turned everything off?
What I notice is that when the units are still fully charged with solar at about 95%, the display shows meaningless values. When switching to 220V, the display is immediately correct.