Hey Leodegrance, I've been having a back and forth with support with no success on the matter. It seems there is a bug with 4.2 where it applies an A-Pose as the default skinning Pose so anytime you paint weights it tries to shift all the weights to the A-Pose.
Hopefully someone from the dev teams reads this and they do something about it cause this basically destroys my entire character workflow and makes the software unusable for my game cinematic characters...
If you find a workaround let me know and I'll do the same here.

Cheers

Having the same issue after importing an .fbx file from sketchfab and converting it (a jacket) to accessory and then to cloth.  In trying to isolate the collar so it won't bend as much, adjusting the weights deforms the mesh in undesirable ways.  I haven't tried in previous versions, (first time attempting this to be honest), so if you get a response or find a work around, please post in this message, thanks!

Hello everyone, I'm trying to edit the weights of my clothes that I've skinned on to my character and when I apply a 1 to my verts for the Pelvis for example, the mesh gets deformed weirdly. 
My suspicion is that it happens because I'm using a custom t-pose to create the clothing in Zbrush and to Apply them on to the model but I didn't have this problem in previous models I've done before CC v4.2.
Because it used to work fine, I assume this is a bug with the latest version but it really messes with my workflow so If anyone has a workaround or if the Devs can look into it, I'd appreciate it!
Below is an example of what the scabbard looks like before and after I apply weights.