Hi Tam,
It sounds like a firmware issue rather than a hardware defect. Please follow the steps in the link below to manually update the SPI firmware first: Radxa Dragon Q6A firmware snapshot
The T3 image you tried is very old. After updating the firmware, please try the latest RadxaOS build (currently T7) from here: radxa-build/radxa-dragon-q6a Currently the latest version is T7.
As for the issue with the eMMC module, could you please confirm the brand and where you bought it? (Note: Orange Pi eMMC modules are not compatible and will cause the board to shut down immediately).