How to determine where "Empty node group" is

I got the message;
“An empty node group has been identified while setting up the simulation. This is most likely the result of having bodies on the structure where the mesh has only one-element thickness on any direction, and has multiple boundary conditions or slave faces of a contact assigned to them. To resolve this problem, you can go to Mesh settings and either try converting your mesh to a second-order mesh or make a refinement on the problematic bodies of the structure. If after trying this the error persists, please contact support.”
I went through all the geometry, contacts and mesh settings. Everything looks OK to me. How can I find where the problem is?
Link to my model:
https://www.simscale.com/workbench/?pid=5322178750660323931

Hello alpatinok,
thanks for reaching out to us here in the forum.

I guess the issue is that the walls of your object are pretty thin, in comparison to your mesh size. Therefore the use of 2nd order elements is suggested.
You can find more information about that here:

Best regards
Sebastian

Hi Sebastian,
Thank you very much for the prompt reply.
I will test this out and inform you accordingly.
Best regards,
Alp