Falling object simulation, imported stl, no collision

Hello everyone and anyone who can help.
I’m a blender noob, literally been using it for week or two to learn new modelling software to add my skills (Rhinoceros 10years experience) and I have come to an problem where I can’t find solution myself with trying or looking online.

I have an extensive library of jewelry STL files and I wanted to try to render one of them in blender with realistic falling object simulation of chain and pendant to an jewelry stand.
Unfortunately when I import the chain and pendant to blender everything works until I try to create the simulation and all object just drop trough the plain I have in the bottom.

I have placed rigid bodies to all of them with collisions on mesh on all of them.
Chain itself has been taken apart to each individual links and origin points placed in the center.
Ground plane is actually solid not just an thin sheet
The simulation seems to work if I create things in blender, but if I import the stl.
I rather use my library that I would not have to create a new one so if anyone knows how to fix it or things I can try it would be great.

Thanks already beforehand

did you find a fix for this?

Hello @Lucas_Psara

No I did not find an solution.
I managed to do a lot of testing and came in the hypothesis about this. What I believe (I can be so wrong about this so please if anyone knows better, please be gentle on your answer) is that Blender does not recognize the mesh as same type of mesh what are made in blender. I also have realized that I seriously lack understanding on blender simulation (plus how much computing power it needs) that realistic over 100 part tiny objects are not ideal when combining my computer and blenders capabilities.

Are you having similar problem?