Any suggestions?
-Apply latest patch for 2.7 and see if the issue disappears. Possibly a bug as you mentioned.
Is there anyway to clear or suppress this alarm if there are no issue reported?
-You could turn off the alarm, but since integration to AD is important it may not be the best idea to disable. You can do so via: Administration->System->Settings->Alarm Settings then under alarm configuration you should be able to set status to disable.