Ax 2009 - Payment Journal Report Slow

We have a client on Ax 2009 and was saying that the Payment Journal Report was slow (not completing).  One person in my group has seen the issue before.  Her solution was:

1. Stop AOS
2. Delete CustVendPaymReport from SSRS
3. Restart SSRS service
4. Backup and delete XPPIL file contents
5. Start AOS
6. Redeploy custVendPaymReport
7. Run Full CIL
8. Run DB sync

I'm not sure why this works.  My colleague seems to think it's because the report has an uncommitted transaction.  However, if that were the case, restarting SQL Server would have solved it.  Also, it does not explain why redeploying the report is part of the process.

I have 2 suspicions, but can't prove either.  One is that the queries involved in gathering the data is missing a needed index.  We tried running the Ola scripts to evaluate and rebuild statistics or reorg/rebuild indexes.  That did not help.  The other possibility is that somehow one of the db temp tables is surviving from run to run when it should not.