Springs: to ground VS simple

Creo 8.0.11

The usage of "to ground" springs is not supported in non linear analysis but linear one is permitted. So I want better understand the main difference between them.

SIMPLE

You can write a function to establish the relation F=k*x.

Only one constant for linear and rotation movements; so if I want the point forced not only in 1 direction, I must lay other springs.

It required two "supports", two ends that gonna be linked with spring.

TO GROUND

You can write a matrix with different direction constants.
Only one side of "ends" to specify because the first is obviously the ground and it's not required its specification.

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QUESTION: Large Displacements Analysis --> why the solver give me an error if I want to replicate a ground sping with a simple spring linked with point and surface?
The first one, the "like ground one", is a point external of the geometry where I've putted a fix constraint (so the ground).

 OK

NOK

To conclude the post, I ask for an explanation to better understand the use of spring with LDA.
Also because I wonder if springs could help to reach convergence in contact analysis.

Please Note: The file attached is a part of a bigger assembly and I used this for some tests (mesh, materials...).

Bye