UPDATE: after a bit of hacking around and the with the hints of the Telegram group I did manage to get into the bootloader.
The procedure actually works, BUT the small (and most important) bit that was missing is the following:

After shutting off the device, turn the device on pressing and holding the power button, wait MORE or LESS one second (the trick suggested by a user in the telegram group was to say "one mississipi") press and hold the low volume button until the logo appears (will appear also the warning ignore it) then RELEASE all the buttons and WAIT! Wait kind of 20 seconds, after that the bootloader will appear. Waiting is the most important part because seems like nothing was happening instead the bootloader is actually loading. This procedure works 100%, once you understand it will be super-easy to do it again.
I hope this will help!

Cheers!

UPDATE: after a bit of hacking around and the with the hints of the Telegram group I did manage to get into the bootloader.
The procedure actually works, BUT the small (and most important) bit that was missing is the following:

After shutting off the device, turn the device on pressing and holding the power button, wait MORE or LESS one second (the trick suggested by a user in the telegram group was to say "one mississipi") press and hold the low volume button until the logo appears (will appear also the warning ignore it) then RELEASE all the buttons and WAIT! Wait kind of 20 seconds, after that the bootloader will appear. Waiting is the most important part because seems like nothing was happening instead the bootloader is actually loading. This procedure works 100%, once you understand it will be super-easy to do it again.
I hope this will help!

Cheers!

@bilb Hi there, I'm having the same issue of @AAM42, I would like to make a clear recap of the steps needed to get back to the bootloader starting from "WARNING: LOCK FLAG IS: UNLOCK, SKIP VERIFY!!" please correct me if I'm wrong (just to clarify I'm still not able to get to the bootloader it's just a summary of what I collected from internet) :

• press the power button, the Jingpad will vibrate and reboot, keep holding and it will shut off without vibrating, it should be off for good. (wait a while to see if it will power on again and in case repeat while it stays off) :ok_button:

• press the power button, wait a second and (keeping the power button pressed) start pressing volume down. This should bring you back to the bootloader menu.

Unfortunately in my case doesn't work, it goes back to the warning so I guess there's something slightly wrong, please give me an hint.

• Is it needed to keep the slate connected to the computer (with or without UBPorts running)?

• After the reboot with the volume down, should the warning be presented again (this is what happens to me)?

• How much time do I have to keep power button and volume down pressed in order to see the bootloader menu? Is it something immediate or requires some time holding the buttons?

• Is there a moment in which the buttons must be released or should I keep them pressed until the menu is shown?

• Is there any small detail that I'm missing in the procedure?

Thanks a lot.