You can start here

SELECT 
    c.Name, c.[Path], MAX(e.TimeStart) as LastRun
 FROM ReportServer.dbo.Catalog c 
    join ReportServer.dbo.ExecutionLog e on c.ItemID = e.ReportID
GROUP...

Try using the query below to get query plan, that might help you with figuring out which procedure is being executed .

SELECT

Try this , tweak the script to suit your needs.

--declare variable, type: table
DECLARE @MyTable TABLE (Input NVARCHAR(30))

--insert sample values
INSERT INTO @MyTable...

Why Would you want to do that  instead of using SQL functions to do your SUM ?

You can very easily generate SQL to do the updates:
[code...

Sue_H is right , maintenance plans don't delete file if they have ".' on the extension. Also check if the SQL Agent account has access to delete in the directory

Great tips
Thanks

Hope you resolved this.

Experienced the same thing all i did was install Latest 2016 SP1

Use Execute SQL Task instead of OLE DB SOURCE , make sure you have a variable for every column so that you can map your Exec SQL task result set...

One file per file group provided you going to put the on separate disks , even the index filegroup should be on the different disk

You can achieve this using a linked server with the query below, just tweak it to use the linked server .

NB:  The account used for the linked server...

On the destination server after migration. OPEN the database master key using the same password as on the source server.

NB : The OPEN command works for the same session...

Great Question .

" Any ideas on where to look to determine why this occurred? "

Jo Pattyn already answered the first place to look at is Windows Eventviewer.