I'm wondering if this is the "disturbed dry solder joints cause UART noise that u-boot interprets as keyboard input" problem I've seen on my own Hub; and has been reported here in the forum with at least one other user. The (fake) keyboard input interrupts boot and drops you into the u-boot local console. If a UART cable is connected and working (which can be a challenge due to the same dry joints) it's fairly obvious when this happens. If no working UART connected the box didn't reach the point where kernel/initramfs (which loads the LE boot splash) was booted so nothing appears on screen .. hence users claim the device is bricked etc.
For the record: I've seen some Amlogic devices with boot states that were challenging to recover from but I've never encountered a device that was truly bricked. And since we (me) have working u-boot for the box, recovery is possible.
The first step is really to get normal UART output to see what happened. Again, if the UART socket joints are dry that might require cable wiggling, patience, and many attempts.