Not only MAC should be added.
If you add new record and firstly add comment then record will be added with blank MAC and clients will reconnect.
So add MAC and interface/forward/... first.
I had such occasion when added blank MAC.
Example, + > select interface (options) or add comment > Apply > insert MAC > OK.
Add MAC first and then make edit.
@ "saintofinternet" i certainly need some help from an indian for an indian. plz provide ur email add and contact info. My email add is firstname.lastname@example.org progress?? a fellow indian asking an indian