SunVisor not snapping back up

Hi, I have a relatively new 2011 Taco purchased back in May. I has around 8000miles on it. When, new, the sun visors have a nice spring action to lock themselves in the up positions but they have been sagging and not snapping back up for the last 3-4 months. Anyone else have the same problem? Any suggestion for remedy? I am almost due for the 10000mile free oil change so I might run it by the dealer but my pass experiences with Toyota dealer have been very negative; they don't seem to know what they are doing!! I had to go back to the dealer 6 times for a simple thing and each time they created another problem that needed additional repair!