The timer process does following tasks:

(1) evaluate time related triggers - every 30 seconds (00:00, 00:30, 01:00 ...)
(2) take care of maintenance status. - every 60 seconds (00:00, 01:00, 02:00 ...)

The process(2) only executed when process(1) start to work at XX:00. So, if process(1) takes 30 -59 seconds, there is a possibility process(2) does not executed.