BUG: Get-ScheduledTask returns NULL for Value of MultipleInstances
If in the settings tab of the scheduled task it is set to "Stop the existing instance", Get-ScheduledTask returns NULL for the value of MultipleInstances. The other three possible values return a string.
Edit the properties of an existing scheduled task, or create a new one. On the Settings tab, change "If the task is already running, then the following rule applies" to the value "Stop the existing instance".
Execute in PowerShell:
$task = Get-ScheduledTask -TaskPath '\' -TaskName 'your task name'
$task.settings.MultipleInstances should be a [string]
$task.settings.MultipleInstances is null
Note that the value of MultipleInstances is available in the CimInstanceProperties:
The value 3 corresponds to "Stop the existing instance".