Current program was modified while running

What causes this issue?

Program &1& has been modified while the program was running.
Since the program is no longer in the PXA buffer, and the version that
was valid when the program was started no longer exists in the
database, the program run was terminated.

How to fix this error?

To analyze the problem further, consult the short dump (Transaction
ST22).

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

Error message extract from SAP system. Copyright SAP SE.