NSM Performer Grand

Hi
Have this jukebox which when turned on shows an error 74, have looked at the error code list which states causes as error during replacement of right side magazine,malfunction grip lever and possible corrections - check alignment to pick up assay and adjust if needed, check function of grip, check function of light barrier OPGRL. Could anyone explain what the error means and what someone would have done before to correct it
regards
seancalla