Over the last couple of days, I noticed that my Powerwalls discharged beyond my threshold in Self-Powered mode, but I didn't think much of it. Today, in preparation for several days of potential adverse weather, I bumped up the threshold to 100% (Essentially Backup-Only mode), but once the sun went down, the Powerwalls began to discharge. I tried switching to Backup-Only mode, but nothing changed - the batteries continue to discharge. Has anyone else seen this? This seems like it must be a bug rather than a unique problem to me.