the first step model you sent has problems with netgen. on import a number of errors show up. it will mesh but in the area of the fillet seam the elements are all mangled. i tried two different mesh sizes and got mangled elements both times in that area. but your 1mm model worked and that was the goal. not really sure what to make of all this. it's kind of like what i was saying. you can follow the same process over and over but get different results. it's not clear what is causing the problems most of the time. so you end up just trying all sorts of things. so a matter of will power to get a good model out. but it seems like it's easier with moi. i look forward to trying it out.

netgen is free and available here, in case you want to play with it; https://ngsolve.org/news/releases

there isn't really decent help for it, but if you have questions, i can try to assist

i attached some pics of the error messages and of the mangled mesh fillet area. this was for the same exact mesh settings i used for your 1mm model.