I am having the same problems. But I just read the update details and it says for Prime4+ which makes me wonder if it is NOT A COMPATIBLE Update for the PRIME 4 and is only intended for the Prime Plus
That’s referring to the Bluetooth portion of the firmware only.
Why don’t you log into your profile on the device and download the firmware directly on there?
You didn’t answer about which track it is that you are having problems with beat gridding?