Whatever those parts are they appear to be broken. I doubt you will be able to plug them back in as they were originally intended.
The knobs suggest that they are involved with something that rotates around. Perhaps part of the pickup roller system or one of the guides. Try running a few pages through the paper path and see if anything gets stuck to help you isolate the problem further.
Or you can use the printer until a problem happens in the paper tray and work your way backwards from there.
Experts are not HP Employees. Experts are advanced users, administrators, technicians, engineers or business partners who volunteer their time to answer community questions.
Please mark anything that is helpful with a Kudo. When you are done troubleshooting, please mark one of the responses as the Solution. This feedback enhances the community by helping future readers choose between multiple similar responses.