Smartshunt current reading wildly different to real current

Hi, I have a new battery bank and want to put my smartshunt onto this, but it’s reading completely different current from the actual current being used.

I currently have it hooked up to a Renogy smart battery with inbuilt bluetooth / shunt, I was using this so I could check the Smartshunt against the inbuilt shunt before I move it the new 400A battery which does not have bluetooth so I have no way of confirming what it’s reading is correct, as you can see below the differences are huge.

Any ideas what settings I have wrong / not configured correctly, I did an initial 100% SOC sync.

Actual current being used from internal battery’ BMS it’s showing 141A load.

Victron shunt via Cerbo GX showing 26.3A

All loads are connected to a 320A buss bar with a single connection from the buss bar to the output of the shunt via copper cables and a single connection via copper cables from the shunt to the battery.