Customer uses an external application to call the API for initiating a transfer.

Occassionaly, he receives the following error:

CAPI_COM_OPEN: Communication Medium Opening Problem

This causes the intended transfer not to be initiated.  However, the next transfer that gets initiated works fine.  

What is the cause of the error?

When there are simultaneous access to CFTCOM file, the API could return with this kind of error because CFTCOM might be blocked by another writer.

It sounds like this might be the cause of the issue since when it reties, the transfer works.

The solution is to modify the application: when the issue happens, do a sleep and to retry.