I can confirm same thing happend to me. As soon as the vendor.bin was replaced, the vertical offset came back. I ran both the self cal and the extended self cal (accessed by tapping on the about menu). The offset was still there. @hubertyoung's upload image has a firmware version of 1.00.
I thought I'd summarize what I've tried:
Push the 924's vendor.bin directly:
The scope identifies itself as DHO924 (max bandwidth 250M) with firmware 00.01.00, at this point, there is an offset on all channels that calibration cannot remove.
Flash the DHO800_DHO900_Update.GEL (I call it OLD.GEL) sits in the scope's file system :
The scope identifies itself as DHO804 (max bandwidth 200M) with firmware 00.01.00, and no waveform display.
Push the 924's vendor.bin again, the scope identifies itself as DHO1074, and no waveform display.
I used build_gel.sh to back up the current version of firmware before everything mentioned above was done. (I call it NEW.GEL)
Flash it and push the 924's vendor.bin:
The scope identifies itself as DHO814 (max bandwidth 100M) with firmware 00.01.06(?), at this point, there is an offset on all channels that can be removed for calibration.
photos can be found here:https://drive.google.com/drive/folders/1mk9uaXJK62KCiBlWOMd4-EZoAnFZniq1?usp=sharing