For clarity, when you say you've done a "factory reset" more times than you can recall, do you mean via the setting menu, or have you used the physical reset button on the device? If only the former, then I'd suggest trying one more true factory reset by pressing and holding the reset button on the bottom (back?) of the device for a full 60 seconds (should only need 30, but better safe than sorry).
The fact that you're the first person to report such an issue here, and that you've had it happen on two devices, is very strange. It's absolutely not a large scale issue, so I suspect it's something specific to the original account the two devices were linked to (which the hard factory reset should expunge entirely), or some bizarre defective batch, if both units were purchased at the same time.
And, FWIW, an SD card should definitely not be necessary unless you've got a lot of larger games installed, but even then, the lack of one should only affect launch time, as the box may need to download the channels on demand.
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