Random Transacations Not Hitting Response Page

[ChanceND]

Every couple weeks we seem to have a transaction that does not hit our Relay Response page after the payment is processed successfully.

Any ideas what could cause this or how to prevent any from getting missed? 

[marine2026]

I think you may need to talk with developer support on this.
1-877-447-3938,,##,,4
As a developer with only a sandbox account, to speak with developer support, you must press ## at the main voice mail menu, and then press 4 to get to developer support.