I got the shifter rebuilt, now it stays in 2nd but comes out of 3rd still occasionally.
> The original Crosley shifter, never had a ball and spring, under the "cork plug". That was there just to keep dirt out.
> The only detents were the 1 spring and 2 poppets, located between the two shift rails.
This article shows balls and springs on both sides of the rails, and an egg-shaped object between the rails.
I think the ball and spring under the plug side would help keep it in third if the Crosley bar has an indent on it there.