Concurrent request shows "SP2-0103: Nothing in SQL buffer to run"

On EBS 12.2.6, I have a custom concurrent request set up with Method = SQLPlus which runs an SQL script on the Linux server. That SQL script calls a DB custom package which has a date-parameter as input which it passes to the package call.

Everything works properly and has been in use for some years, but I just noticed that the Output file contains one line "SP2-0103: Nothing in SQL buffer to run" and the package body doesn't even try to write to fnd_file.put_line(fnd_file.output...), only to fnd_file.log.

I went ahead and added some lines to put to fnd_file.output, and they show up, but after the SP2-0103 error. Does anyone know what I could check to see where this is coming from?