Your smartShunt “Charge detection voltage” is set to 14.4V but the MPPT is only charging to 14.2V Absorption. The Shunt will never reset its internal SOC if the voltage is never reached.
If the MPPT is correct at 14.2V, then set the Shunt “Charge detection voltage” to 14.0V, 0.2V under the Absorption voltage.
The “Charge detection time” is also very long with 40min. Set it back to the standard 3mins. The rest looks good.
If the reset to 100% then happens too early, then adjust the “Tail current” down. 4% of 300A(h) is 12A which could be a bit high, but try it out first
