It does appear that your study setup is unstable in some way. I went through a quick stability diagnosis in a duplicate of your study like this:
1. Go into the study 'Properties'
Turn on 'Use soft springs to stabilize model'
Turn off 'Compute free body forces'
Turn off 'Large displacement mode'
2. Suppress all loads and apply only gravity
3. Mesh/Run the study
4. When the solver stops due to large displacements and prompts to put the study into 'Large Displacement mode' declined this offer. The solver will dump what results it has so far
5. Inspect the displacement plot in the results to find the unrestrained body
The results showed one body was not attached to the rest:
You will want to add some connections/bonds to this body to attach it onto the rest of the model. Once you have done that you would iterate the stability check to see if other bodies are also detached.