ipsec vpn tunnel with Kerio control

keep getting this on a regular basis, some days none some days 5-6 times

2019-06-11 01:13:43 pm UNREACHABLE sitename

tunnel is down for about 10-15 seconds after getting that

does UNREACHABLE mean can not see the other end of the tunnel due to internet congestion?

or is there a setting I need to look at on the tunnel config?