RB751U-2HnD does not work properly with hotspot

RouterOS 5.20

The problem occurs when few active hotspot users connect via wi-fi
For example. When 5 people are connect to hotspot, sometimes CPU usage dramatically increased to 100% by “flash” and a little later the router reboots by watchdog

Please help.

what are those wireless clients: laptops, smartphones?
It reboots when there is lot of traffic?

Ive not seen this, and we have in excess of 1000 751s in the field. Can you replicate the issue every time?

wireless clients is a laptops, but through wds repeater (dd-wrt with MT support) All works fine. a cpu usage about 20% but suddenly increase to 40-100% and router can’t response properly. maximum traffic through wlan is not more than 4 mbps. and yes, the issue repeats often.