My RRS 2010 has rear right corner sitting low.

The vehicle was taken into a dealer for diagnostic in November. They confirmed they had greased the rear right height sensor as this was the issue all within the initial fee.

Now I have the same issue. Do i take it back to them and pay another fee or insist they should have replaced the sensor in the first instance?

they were doing you a favour, to see if a bit of grease would sort it, while the car was on the ramp.

So, no you aren't being reasonable, unless it was under warranty at the time