Unstable Wifi, what is the reason?

Question

Computer networks

I have a mikrotik rb951g-2hnd router with the latest firmware. Everything is connected via wifi. There is a computer (in another room), the ping to the router floats from 1ms to 1000, very often the ping just disappears, sometimes the connection to the network disappears, the signal level is normal. All other devices work without problems, the phone next to this computer opens pages when the computer can't even ping the router! The network on it periodically stupidly lies, on all other devices - it's normal. The computer has a wifi adapter tl-wn722n, I tried to change it to ASUS USB-N10 NANO, it did not help. There are no wireless mice, no microwaves, no other networks on this channel. I tried to put the Wi-Fi adapter in both usb 2 and usb 3, zero sense. PSU on the computer is normal, there are no other problems. On a windows 8 computer. What is the reason for these oddities?
update the problem was solved by turning on the adapter through an extension cord. next to the system unit are a UPS and an av receiver, when you turn on music, for example, the connection drops, apparently this electronics influenced.

Answer 1

In a similar situation, I was saved by replacing the antenna with a similar one. The first was a factory marriage.

Answer 2

Unstable signal most likely.
Install an adapter with a good antenna.

Answer 3

In general, I decided to insert the adapter through an extension cord and the problem went away ..

Answer 4

And it also happens if the USB power on the board floats.

Answer 5

wifi module replace or antenna on it