If that were the case, wouldn't the problem have shown up with the first fillet, not with the last? Also -- all the fillets on the other side of the object were successful.
Here are my current tesselation settings. I will bring them down to 0.1%
I just tried to increase the fillets to 1.00 but I got the same error message: BSplCLib::Interpolate So changing tesselation had no effect.
I see something else too: 2 seam lines appear just where the fillets bump up against the fillets made in Sketch for the Revolution.
What I can try next is going into Sketch and reducing the fillets in the main pulley by 0.5.
Since all the fillets in the main pulley were constrained to equality at 3.175, subtracting 0,5 = 2.675 for all of them.
It looks like that worked. I was just able to increase the fillet size back up to 1.0mm. There were no error messages.
If this were rocket science, making a change like that might be bad, but in architecture, you could probably get away with it.
https://www.dropbox.com/s/s3ffjqlkrw6mv ... fcstd?dl=0