The net:
mikrotik ->ether 1 and 2 WAN , ether 3 to switch(DHCP1), ether 7 to router tplink for wifi (DHCP2)

Details:
After non stop work(16 days), the router Mikrotik lost DHCP2 internet conection. Tplink had no access to internet.
Tplink had access ping only to WAN1,2 gateway!
I try to connect to tplink in outside(Tplink was forwardet) without success!
I try to restart DHCP2 without success!

The solution:
Reboot mikrotik!

Device info:
routerboard CCR1009-8G-1S, packege 6.38.7

The question:
Does anyone have an explanation?