Flourescant lights flickering

The switch, the ballast, starter if it uses one, any one of these items can go out seemingly overnight especially the ballast or starter. I'm betting on the ballast.

There is nothing wrong with the switch or your wiring. The Leviton R01-PR180-1LI is not designed to work with flourescent lights. A lot of electronic controls will bleed through a small voltage when in the "OFF" state. It's just enough voltage to make the ballast in the flourescent light try to fire but not enough to let it fire the way it is supposed too.

What you need is a motion switch that is rated for flourescent lights, such as this :-( :
http://www.smarthome.com/2520W/Leviton-ODS10-IDW-Commercial-Grade-Wall-Mounted-Occupancy-Sensor-White/p.aspx

You could try switching the bulbs and see if the left light still flickers, If so then you have a bad ballast. If not the bulb is going bad.

starter cap in the light base. usually a silver metal or white plastic can. twist it to unlock it and pull it straight out. replace it with the exact type. you can get them at any hardware store. if your light doesn't have one, you'll need to replace the ballast inside the base. if the hardware store does not have one, you'll have to look online. try www.partselect.com.

#1 cause is a bad lamp,try changing that 1st, 2nd if they are two lamp fixtues you ballast could be going bad/or is. Another solution could be you have a loose common/neutral which is normally the white wire @ the light itself of if it is junctioned @ your switch. I would check those items befor spending the money for a new switch. hope this helps.

What you do is cut the wires from the old ballast that feed to the fixture end connectors then 'wire nut' the new ballast wires to the old wires.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/craig_3fa289bf857b1a3c

Compact fluorescent bulbs do not work on dimmers.  You have to use standard incandescent bulbs or not dim the lights.

I believe that unit has a ballast tucked in somewhere in the compressor compartment. It may be easier to access from the back of the unit. I don't think it has a starter.

I find that often this is resolved after has been on for a few minutes as the tube warms up.
Particularly true in current cold spell !!
Pete

The ballast is a device that utilises and expanding/contracting electromagnetic field to create the high voltage which is needed to run fluorescent lights.

It is normally found behind the front cover or reflector part of the fitting and looks like a small box.

Replacement should normally be done by a person qualified in this field.