RFC Error: Backend processing abnormally ended (i.e. exit debugger)

What causes this issue?

A Remote Function Call (RFC) to backend system terminated with a system
failure exception.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Problem root cause is the request processing in backend system has been
abnormally terminated. This can happen when you are debugging the
processing but then exit the debugger and application.
If this is not the case, run System Log (transaction SM21) or
Development Traces (transaction ST11) to find out the root cause.
Contact SAP Support if you can't solve this issue.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.