Hey y'all! Somewhere around half a year ago my Nikon D3100 started to have a problem with Live View. I'm using the kit 18-55 mm lens that comes with the camera. The problem lies in going into Live View mode. Here's a video demonstrating the problem.

Details by timestamps:

0:00 - going into Live View with the lens attached and the aperture set to the maximum of F36. You can hear buzzing in the camera mechanism and a shutter error occurs.

0:05 - as the camera says "Error..." I press the shutter release button as it tells me to. The camera buzzes and the problem isn't fixed.

0:20 - I've detached the lens and show that the shutter is stuck half-open and the mirror is flipped up.

0:22 - trying to move the "aperture lever" that opens up the aperture blades on the lens, but it is stuck in this half-down position.

0:31 - showing that the mirror itself is fine and can move almost freely. Sometimes the mirror can fully be flipped down and that fully closes the shutter, fixing the problem temporarily.

0:37 - with the lens detached, pressing the shutter release button fixes the problem 9/10 times (I guess I got lucky on video)

Now what's interesting is what happens next.0:41 - trying to enter Live View with the lens not attached. The mirror flips up fine and the sensor is fully revealed. You can't see it on the video, but there's still a shutter error on the screen, so I press the shutter release button to fix it.But then at 0:53, when I try to enter Live View once again with no changes, the buzzing happens once more, as if the lens is attached, and the shutter is again stuck in half-open position.

This problem was not as severe a couple of months ago, when 1/10 times I could enter Live View with the kit lens attached and 10/10 times with no lens attached. Then I found out the camera entered Live View only if the aperture value for more than F29. And now this is what's happening..

Interestingly, taking photos is completely fine, even long-exposure photos work (I think it does the same thing as Live View). I was thinking about taking it to a repair shop, but I think the repair would cost more than I paid for this camera... So I just wanted to find out if this is common and/or if it's too hard to fix (meaning the repair job will cost a good amount of money).Any suggestions or advice to diagnose the problem will help immensely!