How to fix nordictrack gx 4.7 recumbent cycle gears slip when pedaling?

It's the clutch bearing in the brake assembly. They can be replaced but you would need a bearing press. Might be better off buying a new assy.

Try to lubricate the treadmill belt after tenstioning. Check the vidoe to know how to lubricate the treadmill.
If you wish to get some details; check the site linked here. Pull up older posts. http://electro-medical.blogspot.com/

Treadmill walking belt lubrication

Try using "locktite" thread lock to help keep it from loosening. U can buy it at automotive or hardware stores.
Or use fingernail polish on the threads as a cheap substitute

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/jan_ed8272c8c2968d14

The shield will not come off unless you remove the entire crank, not just the pedal. to do this, you need to buy a CRANK ARM PULLER TOOL available for around $15.oo at any bicycle shop. Make sure to get one for a square tapered bottom bracket. Just used one, the crank came right off and the shield simply lifted away. here is a link to a YouTube Video showing the tool and explaining the process: https://www.youtube.com/watch?v=N63ofGcRCYQ

did you ever get this fixed ours doing the same?

Did you ever find a solution to the dashboard of your Nortictrack 5.0?

https://support.nordictrack.com/exercise-bike-support/

Prepareto oil by filling a grease gun with lithium grease. Check your owner's manualfor the exact type of grease for your unit.