Just a couple of thoughts....
Unless the batteries are new, do you still have a 900 AH bank? Likely not so a 50% discharge on on the SOC (depending on the device) may actually be a much deeper discharge than 50%.
The inverter/charger also has a setting for the max amps that it will provide in build charging. 900 AH is a big bank and iirc that charger has a max charge rate of 125amps. Look up your own battery specs, but I would bet that your bank could handle the full 125amps so you may want to check to be sure that it is set to deliver all of it.
Finally, look up the charging profile for your batteries and go through the process of setting a custom charge profile in your charger that matches the charge profile of your batteries.