Hi,
I have RB450 configured as firewall & router at my office with RouterOS 3.15
ether2 configured as LAN (local) interface with IP address 192.168.1.1/24 directly connected to switch.
sometimes i can not ping 192.168.1.1 from my PC 192.168.1.15 (sometimes request timed out, sometimes >100ms, but normally it should be <1ms) which makes whole local network (192.168.1.0/24) cannot connect to Internet. 
After i connect with MAC Winbox (thru ether1) and then disable and enable ether1 (LAN) the interface is back to normal again.
Is anyone experienced with this problem ?
Thx for any help. 