Having to jiggle the linkage might be because one of the plastic bushings in the linkage is worn or has fallen out, lay under the car while somebody manipulates the linkage and look for lost motion in the linkage.

Also, it's not uncommon for the shaft in the "detent lever" to come loose and result in lost motion; check for this by disconnecting the linkage from the shift lever and operating the lever by hand...there should be no lost motion between the clicks.