The modules/icinga/files/icinga-downtime script expects 2 lines of output from the Icinga log when applying the downtime.
If the host is already in scheduled dowtime and the purpose of the run is to extend it's downtime adding a second one, the Icinga log will have only one line printed, the second one will not happen if the host is already in scheduled downtime.
[1473416031] EXTERNAL COMMAND: SCHEDULE_HOST_DOWNTIME;mw2132;1473416026;1473423226;1;0;7200;marvin-bot;Reimaging: T143536 [1473416031] HOST DOWNTIME ALERT: mw2132;STARTED; Host has entered a period of scheduled downtime