You must change this setting to something like 1.05 because a setting of 1.25 is the exact cause of your problem.
Your understanding of Peukert is only half correct. For a Peukert of 1.25 at high discharge rates the SOC drops faster than the Ah as you note. However, for low discharge rates, the SOC drops more slowly than the Ah which is your exact problem. Peukert works both ways.