Cause:
2018.1 SU1 added the "Task Overrides" options in the scheduled tasks properties window:
This was added to allow software distribution to not be beholden to the maintenance window on the agent. For Patch tasks, the "Ignore Maintenance Agent Settings" from the main properties window to the new "Overrides" section.
Solution:
If you want your tasks to respect the maintenance windows of the devices Patch and Compliance agent setting, make sure that you uncheck the "Ignore Maintenance Agent Settings" on your existing and new scheduled tasks.