Looking at the cell voltages and your settings in an earlier post, to me it just looks like battery #1 hasn't hit the 3.475V you have set for cell 100% and hence hasn't 'reset' itself to 100% when at (virtually) full charge.I will get this figured out.
Not sure when your charging system actually stops charging the 3 batteries (does it stop when 2 out of 3 batteries get to 100%)?
Either way, maybe reducing the cell 100% and full charge settings to, say, 3.45V will then allow BMS #1 to get to that voltage and re-calibrate back to 100%?