So I just took the bike out for a ride, and if I shift into first 5$3 shifter stays down. Then if I bring it to 2nd, it stays up. It doesn't want to "spring back" to it's normal resting position.

Anyone know why this is happening? Bike has been running great until now..

 

Check the shifter linkage, front and back to see if it's binding.

 

Did you ever change the shifter? There is a black rubber ring that keeps the shifter axle from pressing in. I left mine off and the shifter eventually was rubbing against the primary and sticking.

 

No, never changed the shifter. And nothing seems to be binding. I don't understand how things like this happen overnight...

 

At highway speeds it seems to work normally, but it returns to it's normal position very slowly..

 

Model and year?

 

2010 Fat Bob

 

Make sure everything is tight.

 

So I put some WD-40 on the linkage and that helped a lot...

 

I had exact same problem, forward control pivot binding.
Read my fix here