Starter battery being drained in DC/DC configuration unexpectedly - help?

As stated in my marine configuration my starter battery is getting drawn down under system load lower than the Input Lockout setting on the Orion XS DC/DC charger and throwing low voltage alarms.

The config:

  • 12v agm starter battery (alarm setting of 11.7v) (4 years old but seems to function fine under all tests)
  • 2x300 AH off brand lifeP04 batteries
  • 1x550w rigid solar panel
  • Victron Smartshunt
  • Victron 50/100 Mppt charge controller
  • Victron Orion XS 50a DC/DC charger

No trouble staring YET, but given we are often in far away bays and anchorages I don’t want to have to rely on the backup battery starting booster I have just in case.

The setup had an starter battery isolator, but I was instructed by victron to design that out and rely on the input voltage lockout setting.

I have attached a couple of settings screen shots in case that is helpful.


Any help appreciated.

(edits for additional information completeness)