Odd SoC adjustment

I haven't seen this type of SoC adjustment before. A gradual reduction from 30% down to 15% over an hour and a half with no discharge. Normally there's a percentage point change when then battery is idle.

I have a Gen 1 3.5 Hybrid Inverter with a 8.2 kWh battery. The battery has been on firmware 3017 for a few months but for some reason a recalibration was kicked off 5 days ago - not by me as I'm on Intelligent Flux so I don't play with the system at the moment.

The 30% SoC figure following the discharge run is too high should have been around 24%, but the 15% figure is too low. Is this just an artifact of the recalibration or is something else going on?

I have a 13.5kWh AIO plus gateway and am on Cosy Octopus tariff. I have noticed the occasional drop-off in reported SoC. This is generally a 5-10% drop in 20-30 minutes without any extra load on the system. I had one occasion of a 32% drop in an hour.

I have a thread in this forum describing my experiences and i have a support ticket open with GE, but i am starting to suspect that the issue is with the battery software incorrectly calculating SoC.

Fortunately I have a large enough battery that I have spare capacity to cope with a sudden 10-15% loss of reported SoC without needing to import any power at other than off-peak times; but it is a tiresome issue and was quite disconcerting at first