i do not see any issue on EEM applet high level.
1. do you have NTP Sync Correctly
2. worth adding if you have AAA in place
event manager session cli username USER
EDIT : ( i did some test here) - Bold made the trickl.
event manager applet Shutdown_Guest-Access_6p-6a
event timer cron name Shutdown_Guest-Access_6p-6a "0 18 * * *"
action 1.0 cli command "enable"
action 2.0 cli command "config t"
action 3.0 cli command "interface GigabitEthernet0/1.150"
action 4.0 cli command "shut"
action 5.0 cli command "end"
action 6.0 syslog msg "Interface GigabitEthernet0/1.150 has been shutdown"
event manager applet Start_Guest-Access_7a-6p
event timer cron name Start_Guest-Access_7a-6p cron-entry "0 7 * * *"
action 1.0 cli command "enable"
action 2.0 cli command "config t"
action 3.0 cli command "interface GigabitEthernet0/1.150"
action 4.0 cli command "no shut"
action 5.0 cli command "end"
action 6.0 syslog msg "Interface GigabitEthernet0/1.150 has been restored"