With firmware 1.00 I did not find the way to properly upgrade my DHO804 to DHO924. The offset is always there.
I tried to replace cal*.hex files, but ended up with no waveform display.
Then, probably after replacing the Key.data file, my scope went into the boot loop.
There was no time to do anything before the reboot. The sparrow.apk was constantly reloading.
In this state, adb worked fine, it was possible to write any files to the scope, but the "/rigol/data/cal_afe_bandwidth.hex" was always replaced by the scope for the same instance before reboot. That was probably some dummy file, which I did not find in any of the firmware copies I have.
So I had to open the oscilloscope, to flash the DHO924S firmware from the first message. And now it's back again, calibrated with no offset.
BTW, the firmware is from DHO924S, but replacing only the vendor.bin gives DHO924 without the "S" option.
UPDATE: boot loop was due to lack of execution permissions on the scripts.