Hi Biricio,
Looking at the pdf to your question, I have several for you actually. First off, this cylinder is part of the system and fully connected to your box, correct? Second, why have you defined the plate that you did as a rigid body? Is this plate only part of itself, leading off of another surface?
If it is supposed to be a more rigid material, I would suggest making a thorough material property file if you have not already.
Are you merely looking for just the deformation here? Or is this a design based analysis?
~ Kherszal