i had some ideas to test. i brought in all the models to netgen and checked to see if those warnings came up. they came up for all of the models you sent me. but two of your models meshed anyways. there were no warnings for the rhino no fillet model and the .08mm fillet model. Also, no warning for my correct 1mm fillet model. you may be getting affected by those bad projected curves that rhino created. i think i posted an updated file that has the fixed profiles in there. and the solid with the fixed profiles before and after filleting. if you try working with that model, the netgen errors should go away. but it seems like those errors don't indicate whether the model will mesh or not. however, netgen seems to work better if there are no errors present, the errors could explain the hanging i'm getting with the models you sent.

when i get moi v4, i will try making the projections in moi. if it does it better than rhino, there may be no issues with filleting and step export. rhino takes my two ellipses and two curves, that have been joined, and turns it into two curves. they break the ellipses up and merge parts of them with the curves. they also re-create the curves in a bad manner. so i have to go back split their two curves to get the ellipses back then rebuild all four curves and join them. the problem here is you loose accuracy doing the rebuild. plus it's yet another time suck. ideally, if the program could project the original curves and keep their structure. rhino can't do that apparently. not sure about moi.