gas gauge issue

[Blue21]

The gas gauge for the right tank, the needle goes to the level smoothly without stopping.
When switched to the left tank the needle is shakey, sporatically quivering back and forth from the bottom upto where it appears to be the level of gas and back down. What would be causing this?

 

[mdoherty]

Loose wire, corroded connection or a bad sender.

 

[Billylll]

All of the above but I suspect a bad sender unit.
Bill