Strange ping and wireless devices lost connection

Good day!

I change Routerbord from RB750U-2Hnd to RB951G-2HnD and found strange problem. My PC is connected by cable and work fine, but ping have same regular latency to 2000ms every 6 pings (saw attachment).

But main problem - that is my wireless devices lost connection and I must reconnect device.

Please help, what is this - hardware defect, or need some software configuration?

I upgrade RB951G-2HnD to Mikrotik OS 6.31 and RB Current Firmware to 3.24.