Upgrade 2860 to latest firmware using RST file (i.e. this does firmware upgrade and factory reset). Obviously jot down all settings prior to doing this as you'll need to reconfigure. Do not restore settings from backup, configure them all manually.
This will rule out a configuration issue.
Regarding DDoS issue simply unplug WAN connection and see if pings to router stabalize.
Ensure Hardware Acceleration is disabled.
ZeN Fibre Unlimited 2
Edited by Pipexer (Fri 22-Sep-17 22:43:54)