First of all a small fixing. As I said uncheck "Ignore morphs already in clothing" in the transfer tab would lead to overwriting these with new morphs, I got a correction by Ralf.
The existing morph will not be overwritten but a additonal new morph will be created though with a new number adding. So clearly to differ from the existing one.

Now for that strange behavior. I'm not sure but dial's not working wether in body nor single actor (I guess your clothing isn't locked as total) could only happen with empty morphs or broken internal settings.

So empty morphs is clear. Only dials as dummys are there and no morph data as such.

Broken internal settings could happen to the connection between body dial and actors dial (holding the morph data). There only a wrong character in text can do that.
But not working actor dials isn't to be done so easy.
And by the internal coding this can stop the dial working but the morph may work via superconforming.

But together with your second behavior the distorting of the clothing, I'm in the opinion that indeed it is a problem with superconforming or better said cross talk.

I can remember to a cloth there the dials didn't work even though it reacted to the figures morphs. Cross talk isn't easy (better nasty) although now used as a legitimized feature.
So having two morphs working to the same mesh region in a very similar way as you would get with MC again copying a existing morph will strenghten the efffect of the morph. And if the first or may be both are superconforming you get to much morphing. And this surely can lead to a mesh "explosion".

So this is one of the point's I'm not such a big friend of superconforming. Also I often get trouble with using more than one figure in images. The internal number of the figures is depending on their loading order. And so often superconforming is making mismatch in using the values of the wrong vicky ... it's what I often got.
So I'm more satisfied with dialing manual or with the use of a script which is getting the right figure and his/her clothing instead of using some weak internal numbering.
Ralf's Copy Morph script from freestuff will do this or the same the loading routines from XL-Library (for this the same coding). But both wouldalso having trouble if two similar morphs are executed at the same time and clothing.

But in this problem than you are really right it's better to delete all existing morphs prior to build them totally new with MC.
Though I love to have clear order in my figures and clothes I did this rarely cause in most cases the given morphs are working well. More do I have the problem that they are not completly given or that no morphs are given.. So I seldom have the problem to replace a given morph.

To have a clear look to this could you give a image how the cloth is looking at the figure and a view to the parameter pallet with morph's settings. This may be best from a actor like abdomen or chest and with P8 if possible cause in P8 the dial's in pallet are showing their original value and the value coming from body.
This may be could help to see the problem best.

And not absolute important but for information was that offerings by one or two vendors or is it cross over equal which vendor. So do we have a vendor's special problem or a general problem of poser which could happen with each vendor's clothings.