If you are experiencing this issue (400mhz, 0.39ghz cpu clock) while charging the battery above around 50+% and want an early test build based on 3.06 that has a fix, DM me on the forum and I can provide a link to download. Otherwise we will be releasing 3.07 in the next week or so.
Technical reason seems to be related to some component variation around the charging circuit. Internally the charger IC has several control loops that run, including an input current control loop, and a battery charging control loop. Both of these limit current, and the input current loop can also limit the battery charging control loop. At a high state of charge the battery charging control loop can allow the input current to increase to the maximum input current, and trip the prochot over a very short time interval before correcting, (microseconds) due to what I think is control lag. The charger has a setting to debounce this, and we increased the debounce time. Still getting some data on the exactly why this happens, but this sounds like a case where a pole moved to the right hand side of the plane