Paper Jams in M607n- 13.B2- Just Replaced the Pick Up and Separation Roller Assemblies

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I am getting paper jamming in HP LJE M607 after replacing pick-up & separation roller assemblies. Before, the rollers were bald and picking up extra paper ever 5 -10 pages. I felt I got the top hook in for the pick-up assembly, but not totally sure. Can any one help me, at least with a hint that the pick-up assembly is hooked in correctly.