In reviewing server logs , have found errors reported when a file was not found during a diff cache. The server settings for remove a file if not found during a diff cache is checked. Will upload a pdf file with screen shots from admin console that demonstrates the issue and questions about when files are removed from diff cache list... before or after error is reported.

Not determined

MDM 15.1HF23

This appears to no longer be an issue in 18.1, but it is still being monitored as of March 2019