On 2023/02/24 at 1:59 PM, Coulomb said:

This is indeed Axpert VM III Twin (= PIP-6048MT) firmware for the '28062 processor (as all VM models use). The handles 1500W, 4000W (both 24 V) and 6000W (48 V) ratings.

If the date stamp can be believed, this was compiled today.

As for the hex file name, they seem to name a lot of them VP5K.hex or VP5K.inv. It seems to me that you would have to rename the hex file to VM3.hex if you wanted to use the USB update option. The reflash tool looks very much like the Arena reflash tool, but maybe the VM reflash tools always did. These reflash tools don't seem to mind what the file name is, so it's odd that they don't name it VM3.hex as the USB update firmware (in the display) wants it.

As for what they may have changed, it will take me a long time to find out, sorry. 

So this firmware fixed grid charging issue

Now in "Solar only" charging priority battery isn't being charged by grid

But I'm curious, is inverter taking power from battery to function even if grid is available? Considering battery discharge rate without using it to power loads - I think this is the case

On 2023/02/24 at 1:59 PM, Coulomb said:

This is indeed Axpert VM III Twin (= PIP-6048MT) firmware for the '28062 processor (as all VM models use). The handles 1500W, 4000W (both 24 V) and 6000W (48 V) ratings.

If the date stamp can be believed, this was compiled today.

As for the hex file name, they seem to name a lot of them VP5K.hex or VP5K.inv. It seems to me that you would have to rename the hex file to VM3.hex if you wanted to use the USB update option. The reflash tool looks very much like the Arena reflash tool, but maybe the VM reflash tools always did. These reflash tools don't seem to mind what the file name is, so it's odd that they don't name it VM3.hex as the USB update firmware (in the display) wants it.

As for what they may have changed, it will take me a long time to find out, sorry. 

Could you tell me how did you unpack the firmware to check the version?
I'm looking at "new" firmware that supports CAN communication, but it seems older than mine (that fixes solar charging issue)
Thanks

UPDATE:

I've retested the issue with real solar panels installed
In the "solar only charging" mode inverter will not charge batteries from grid only if there's zero solar power available (exactly 0V measured on PV terminals)
But as soon as a tiniest bit of sun shines on panels -- it will start drawing 1-2A from grid (charging with 300-400 watt)
So the issue wasn't really fixed, just a hack for 0 volts PV applied