Dell Latitude 7320 Detachable bad performance on battery after Bios update

Hello,

I have started to have performance problems with my Dell Latitude 7320 Detachable when updating my Bios from 1.27 to any newer version. The system works perfectly fine when plugged in to a power source or docking station. However for any new update, when run on battery without any other device attached, the CPU performance is limited to 0.5 GHz, which results in the system not being usable.

My current approach is to downgrade to 1.27 from any of the newer Bios updates. Does anyone has similar issue? I have seen on the forum similar symptom, but with a USB devices connected. This is not my case, the CPU is limited to 0.5 GHz once it is disconnected from the power source anytime.

I have tried clean OS installation, Dell has replaced the board, we have played with the Bios settings - but it feels it is more Bios issue rather than a HW issue. Is there anyone who has been facing the issue and has been able to resolve it with the latest Bios updates?

Thank you for any recommendation.