@miy I had the same problem as you and I believe I posted how I resolved the bootloop in the Jing forums. But they are gone now.

It seems to me that when you want to shutdown the JingPad when it is in this state you have to hold the power button in and wait for two things to happen. 1) the familiar buzz and 2) about 10 seconds or so later you'll see something flash across the screen. This is when you release the power button.

Wait a few minutes before trying to reboot into recovery. When you do boot to recovery I find pushing the power button + 1 second then volume down and wait for the Jingpad logo then release and wait 20 seconds or so. You should have a recovery menu.

It has been a while since I had to do this and I'm working from memory. I've pretty much given up on UT on the JingPad. Good luck!!!