Have you adjusted the BMV settings particularly the charged voltage. The default setting with solar charging, (especially at lower light levels) can result in the SOC synchronizing to 100% before the batteries are full. Have you also reduced the capacity to 500Ah. The attached FAQ covers the correct settings.
A second FAQ covers wiring, the chassis connection is often a source of errors on RVs and boats resulting in some loads not being measured, so the batteries run out quicker than the SOC suggests.
Are your batteries balanced, hopefully you have Bluetooth batteries so you can see individual cell voltages. An unbalanced battery will display as 100% SOC before it is full and have low voltage before the SOC says it is empty. Unbalanced batteries have a lower effective capacity than nameplate. Cold batteries also have lower effective capacity.