Ram slot

If you're certain it's the slot that's bad and not the module, the solution is a replacement system board.

Test to see if the issue is the slot or the RAM stick.

Disconnect the AC adapter.
Disconnect the battery.
Press and hold the power button for 30 seconds to discharge any residual electricity.

Remove the RAM sticks.
Use a soft rubber eraser (the type used to erase pencil) to clean all the RAM contacts on both sides. Use a clean cloth to brush off any eraser residue.
Moisten a microfibre cloth with 99% isopropyl alcohol and use a credit card to slip the damp cloth into each RAM slot to clean its contacts.

After everything is dry, insert one RAM stick firmly at a 30° to 45° angle into the slot you think is good, ensuring that it seats fully in the slot.

Connect the AC adapter.
Boot the laptop and run memory diagnostics.

If that works okay, then try the RAM stick in the other slot (the one you think is bad).
Disconnect the AC adapter.
Disconnect the battery.
Press and hold the power button for 30 seconds to discharge any residual electricity.
Insert the RAM stick firmly at a 30° to 45° angle into the slot you think is bad, ensuring that it seats fully in the slot.

Connect the AC adapter.
Boot the laptop and run memory diagnostics.

If, after cleaning RAM sticks and slots, a stick works fine in one slot and fails in the other slot, then you will have confirmed that you have a bad RAM slot. In that case, that would require a new motherboard.

Whenever handling RAM and touching internal components, wear a grounded wrist strap, also called anti-static wrist strap, ESD wrist strap, or ground bracelet. I know many people do such work without this, but it's a cheap and sensible precaution. Rest the laptop on an anti-static mat or at least a reasonable alternative such as corrugated cardboard.