Why a simple Godot "SoftBody2D" is not working

Question

I'm working on creating a slime player character and want it to look similar to a SoftBody2D. Since Godot doesn't have a SoftBody2D by default, I made one from scratch and also tried using the SoftBody2D-addon. However, due to structural or gameplay issues, it doesn't work as expected. The RigidBody2D objects (which I'll call rb particles) either separate, block the main body, stick to the floor, walls, or platforms, or stretch until they form two bodies linked only by a thread. This prevents typical player actions like moving or jumping.

I'm stuck and unsure what to do. I don't need a perfect softbody simulator, just something that visually resembles it. Ideally, I'd like to use only RigidBody2D spheres. After four days, I'm still going in circles. I haven't included any written code because it involves a complex scene with many joints and an addon. Instead, I've provided a minimal project showing some of the problems and an image. Any help is appreciated.

project_github