Excellent suggestion - thank you!
My problem seems to stem from an API error resulting from my (mis?)use of {JOB(Active,LastExited,M/d/yyyy h:mm:ss.ff tt)}
9/5/2017 12:27:32 PM Err API->"[Error in SetVariables, string: {JOB(Active,LastExited,M/d/yyyy h:mm:ss.ff tt)}, err: Object reference not set to an instance of an object.]"
9/5/2017 12:27:32 PM Debug DateCheck (\\cmfs01\Users\Shared\PRGTickets\720\Partner.720387622.1504274536.001.pdf), dteNewerThan: 0001-01-01 00:00:00, fi.LastWriteTime: 2017-09-01 09:14:27, fi.LastWriteTime.ToLocalTime: 2017-09-01 09:14:27
... etc.