In a printing system for producing a print job, the printing system including a print engine for imaging regular substrates, fed to the print engine from a regular substrate feeding apparatus, and delivering the imaged regular substrates as an output, the print engine being operatively coupled with a special sheet insertion subsystem, a special sheet insertion path passing by the special sheet insertion subsystem, the special sheet insertion subsystem being adapted to hold and feed special insert sheets into the special sheet insertion path so that one or more special insert sheets are interpossible with the delivered output of imaged regular substrates, a series of spaces being formed in the delivered output of imaged substrates for receiving first and second special insert sheets from the special sheet insertion subsystem when the first special insert sheet is fed from the special sheet insertion subsystem at a first scheduled point in time and the second special insert sheet is fed from the special sheet insertion subsystem at a second scheduled point in time, a method of controlling the feeding of the first and second special insert sheets comprising:
- a) feeding the first special insert sheet from the special sheet insertion subsystem to the special sheet insertion path, at the first scheduled point in time, so that the first special insert sheet is disposed in a first one of the series of spaces to form a gap between one of the imaged regular substrates and the first special insert sheet, the gap having a magnitude associated therewith;
- b) determining whether the magnitude associated with the gap is within a predefined tolerance;
- and
- c) when the magnitude associated with the gap is outside of the predefined tolerance, rescheduling the second scheduled point in time.