Rigid Bodies reacting with each other terribly :(

Hi BA crew, got a seemingly common issue here with no common solution…

Apologies in advance if this is dumb, I am clearly quite new to blender!

So I am experimenting with interlocking objects however when I try to animate in order to simulate how the objects fall under gravity, they go bananas and spin off into the distance.

I have read dozens of forums and watched a lot of videos, tried it all but to no avail. I think that the issue may be because they are designed as perfectly interlocking objects with lots of surface contact, but that seems nuts…

Does anyone have any ideas what could cause this?

Here you can see three of the same object, they are designed (in Rhino) to interlock perfectly. They are manifold happy meshes (I believe).

The rigid body settings for each are as follows, mesh collision shape etc.

I have set their origins to centre of mass (volume). I do change the origin a lot in order to accurately snap them into location (using the 3D cursor). But before testing I reset the origin to centre of mass. This does beg the question, should I apply the location transform? If I do that the origin resets to 0,0,0 giving even weirder animation results.

Mass is calculated using concrete and verified using some basic densities and the volume calc.

Not touched the scene properties.

The ‘floor’ is a passive body, box collision shape.

Here’s a wetransfer link to the file if interested:
https://we.tl/t-O9a59j6ea4

Any assistance or thoughts would be super welcome!
Cheers,
A

I just found and answered here

and in the last answer ther is something like:

… join the 9 blocks together into one object. Then, turn on self-collisions

Maybe this trick is here usable here too ???