This is how the BC should be setup.
Remove the fixed condition on the bottom. It is wrong.
Setup the symmetry planes with a symmetry or sliding face condition.
Setup the bottom with a sliding face condition.
Doing this will constrain all 3 dof for translation and all 3 rotational dof.
Is your intent to have such a massive interference fit? That will create difficulties for you.
You may need springs to help the cap on top to initiate it's contact.
436_symmetry_bc.jpg 192.5 KB
In the meantime I read that for multiple face selection, one had to define one circular symmetry for each "couple".
But thanks for the hint about how to properly constrain the DOF in my problem.