Can't answer your question since I no longer have a 822A. But I can tell you from the past that some firmware versions work and some firmware version don't work.
What I did in the past was to x-flash the DW822A to a EW822U and run the external firmware with no problems at all. Only negative is that BenQ updates this firmware less than the 822A. But think about it, the 822A is old now and I can see BenQ doing very little updates in the future.