Fuel Gauge - Inaccuracy

[iano]

Hi All - I have dodgy fuel gauge - showing 3/4 full , when full - then hangs around on the R range for a while after about 300km
I have access to the sender unit - Are there any tips/ tricks that I could do to it that might help with accuracy? -
Ta Ian
(NSW, Australia)

 

[67panel]

Is it a tube one? if an arm one then bend the wire and check the float is okay.