I just recently saw this when I ran the firebird backup gbak:readied database e:\emr\clinical\REMR.FDB for backup gbak:creating file e:\emr\clinical\cache-listener\remr.fbk gbak: ERROR:cannot open backup file e:\emr\clinical\cache-listener\remr.fbk gbak:Exiting before completion due to errors which is caused by some process locking the remr.fbk file so that it can't be overwritten. It may be the sfk program doing this, so just change the target file to something else until I sort out why this might happen.
Yes, it is the sfk ( swiss file knife ) which is remaining resident instead of closing down. It looks like it's asking permission to overwrite, so we need to add a -yes to the command line.