Hi,
I had the same behaviour earlier today.
I have two 8.2 batteries hooked up to a 3.0 AC inverter.
The primary was installed last August and the Secondary last Wednesday.
Commissioning went well and everything has been running smoothly since ... until today.
My primary seems to have dropped its SOC down to zero from 100%
My primary battery is DY2219G082, on 1%
The secondary, on 100% is DY2218G702
Both batteries are on 3012
The primary has run smoothly since installation last August but it did experience 2 SOC drops to zero last October, running on 3007.
Like you, the batteries have been tracking one another by 10-15%.
I am on Octopus Flux and have been exporting and importing to the full amount each day so the battery SOCs have been getting a some good practice from 100% down to 35-40 %.
Everything looks fine on the portal and App. All 4 green LEDs are on for both batteries.
But looking at 'more information' for the batteries on the app shows the sundry at 100% and primary at 0%
I haven't tried a power off and on cycle for batteries and inverter.
I intend to do a 'full export' at 4 pm today and will see what happens.
If nothing changes, I will try the On/Off cycles.
Rob