h, and using the BScale and BDistance are creating havoc somehow too. I've simplified first, and used the Kangaroo Frames component along with setting internal iterations, to make MeshMachine act like a normal component, along with releasing the FixC and FixV. The FixV didn't make any sense anyway. I've also set Pull to 0 to speed it up during testing, since much less calculation is involved to just let the meshes collapse, prevented from disappearing altogether by using a mere 15 iterations.
Also, your breps are open so that allows much more chaos and then collapse, though they did manage to close themselves too at times. Here is closed breps with a full 45 iterations:
So now that it's working, lets re-Fix the curves, and the problem arises that there is an extra seam line that is getting fixed too, running along the cylinder, stopping the mesh from pulling tight under tension wherever a vertex happens to be near that line:
So lets grab only the naked edge curves instead:
And what happens if we lose the end caps, now that we don't have an extra line skewing the result?:
There is no real curvature differences since it's not a curvy brep so the Adapt at full 1 setting has little to do. Now what does the BScale and BDist do? Nothing! Why? Your scale is out of whack, 99 mm high cylinders but only a falloff maximum of about 5, so let's make the falloff be 25 instead, but I must restore the end caps or the meshes collapse away for some reason and freezes Rhino for a minute or so the first time I try it:
It's a start.
If I intersect the cylinders, nothing changes, since they are being treated as separate runs. MeshMachine outputs a sequence of two outputs though, due to Frames being set to a bare minimum of 2 needed to get it to work, so I filter out the original run, which is just the unmodified initial mesh it creates.
The lesson so far is that closed meshes are much less prone to collapse and glitches leading to screw ups.
A Boolean union of the cylinders is when it gets funner, here show with and without the fixed curves that seem to define boundaries too where really there are just polysurface edges:
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