It seems to me that worn bushings would have the opposite effect. Because of the excess play in the linkage caused by worn bushings, any undesired motion would be neutralized because of the play afforded by the worn or absent bushing and therefore not affect the shift handle.
I'd look toward the above transmission mount suggestion causing the motion while at the same time I'd replace the bushings if needed. Worn bushing will give you a misreading on the gearshift lever and keep the trans from engaging... rather than cause the car to pop out of gear.
1993 190E 2.3
2000 Toyota 4x4 Tundra