Are you sure about the fact that printing is done using this failed output type only? Ideally, output doesn't get executed if it's in failed status(red sign). You will have to check following things to get to the root cause of the issue.
1) Make sure your output configuration is setup correctly in NACE or not. Spcifically, form & program name.
2) Check if sy-subrc is not getting set to non-zero value when you come out of output print program.
3) Debug the output print program by setting up external breakpoint & switching on update debugging while saving a document in VF01/VF02 transaction.
4) You can put breakpoints at 'NAST_PROTOCOL_UPDATE' FM in debugging mode and once breakpoint hits, you can find out the source of error. This FM updated the error log in NAST table.
5) If none of the above option works, you will also have to check if there is any output control routine from VOFM is assigned to this output type or not. Failure of output control routine also fails the output type, but it also restricts the document printing.
