Unable to union solids composed of closed breps

I’m unable to union solids composed of closed breps as shown below.

I tried HS_Kim’s method to reconstruct each solid, yet it still doesn’t work.

The solid union is not working even if the objects are baked to Rhino.

May I ask what might be the source of this problem and what might be the solution?

Thanks.


unable to union solids.gh (93.5 KB)

Hi
I’ve located your problem but have no idea why it fails
The purple bois are unioned already but the blue one fails.