<error> on setting a parameter in an action

I am having problems in a policy action that run daily where endpoints gradually return on a line of the action where a parameter is set. It can start our with a small set of endpoints returning where the parameter is set but overtime it grows to hundreds. Ex.

parameter "SchtasksDetail" = "{pathname of parent folder of client}\__BESdata\__OSMaintenance\schtasks.txt"

I have had the relevance "{pathname of parent folder of client & "\__BESdata\__OSMaintenance\schtasks.txt"}" as well and it does the same thing.

I can issue a separate action on those same endpoints that have previously returned on that line of the action and run in a new action and they will execute the action without fault.

Does anyone have any ideas what might contribute to this? I should mention this happens on 8.2 and 9.1 client endpoints alike.

Sorry the is returned in the action preceding the parameter and the other lines leading up to and following the line have a blank ahead of them.