DHCP GUI stops working after CLI edit of DHCP entry

I have a strange problem.

DHCP server on interface works fine and show all in gui when configured through the GUI.

making a change using the CLI on this dhcp server disables the DHCP GUI monitor.

the entry added was the DNS domain name for this scope.

restarting the DHCP server does not help after removing the DNS domain name, GUI still does not work.

FortiOS V5.6.6 build 1630 - Fortigate 200E

Anyone experienced similar problem and is there a solution?