If Spring And Damper are > 0, did you try change Spring and Damper (X, Y)?
Path: Configurable Joint → Linear Limit Spring
Configurable Joint → Linear Limit Spring
Set:
Spring = 10000 (or higher for stiffer constraint)
Spring = 10000
Damper = 100 (or higher for faster stabilization)
Damper = 100
Linear Limit?