Shuts down or reboots from usb?

Question

Iron

Good time everyone.

Faced with an unusual situation restarting the PC.
A usb cable is connected from the monitor to the back of the motherboard to connect flash drives, a phone, and more.
Sometimes when you connect the phone, the computer reboots.

The same situation with usb on the front.
It doesn't always happen.

Motherboard changed the effect is the same.
Where to dig? BP? Frame?

Answer 1

When plugged in, it has a short on the case, the PSU perceives it as a shutdown / reboot command

Answer 2

Corps, IMHO, hardly.
The next step is to check / repair / replace the PSU. USB power, by the way, from which PSU line is it supplied - 5V (on a switched off PC - no) or 5Vsb (on a switched off PC - yes)?

Answer 3

Replacing the video card seemed to help. A couple of weeks the flight is normal.
I'll keep you informed.
The VT100 answer really helped at first, I really thought everything worked out.
I'll give it a Like from the bottom of my heart.
Thank you.