Hello Rogers, behind the pick up that takes the paper, there is a flag sensor (paper step sensor flag), to access it you have to remove the covers, and the metal plate. Behind this is the mechanism, a flag works to sense the passage of paper and another flag for the cartridge, both in conjunction with an optocoupler that is activated by these flags, sometimes some of them are dislodged and prevents it from returning to its place after the passage of a leaf. this to comment, there are other tests to follow, comment on how it goes, best regards I enclose an illustrative image of the location of the sensors: