Not sure 100% sure Im following the issue you having but I have always found that on a model when I create a weight map and nothing on it has full blackness then it completely falls off the character like yours is.
I find that when some parts of the models weight map has some full blackness then it stops falling off the character.
In this image I am showing where I think I would set yours where the weight map will be fully black so it wont flow and the rest of it I would make the rest of it flowable.
I don't know if that's how you did it? I just find as I am saying here that if I make all of the model flowable then it completely falls of the character and I thought I would just say it here in case it might help you.
If not then sorry for adding this post.

Here is a demo of what I am thinking because of seeing you model fully falling off the character
Here is 2 weight maps I made 1 bad and 1 ok but should be made better...oh well just showing what I am saying.

Ok add the bad one to a model

and here is a video showing that it falls off the character like yours does.
So now I add the better weight map

and now it works better although like I said it all needs to be made better than what I am showing here. Just did it quick to show how to stop it from falling off the character
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