How to fix high ping between laptop and router over Wi-Fi?

Question

WiFi

So, question.
I started to lag the Internet, immediately checked the connection between the router and one laptop with a ping. Then with another. If normal for my apartment, the connection is in the region of 3-5 ms at the peak, but now the ping jumps from 10 to 3200. There are no losses.
The channel is worth 6, as the most not clogged (checked)
Authentication method: wpa2-psk
Clients: 5
NAT works.
Traffic between clients is about 10MB at peak, now - about 100kb
Compatibility mode: B/G/N mixed
Modem: DSL-2640U

Answer 1

1. Hard reset
2. Flashing to the latest stable firmware from FTP