I’ve run into something in v2.55 I don’t remember experiencing in 2.4x – it seems that a vertex group set up for pinning a cloth object is having its vertex weights modified by global auto-normalization of vertex weights that takes place out of user control (this isn’t the same as the Auto-normalization option used with weight painting).
If the mesh has vertices in the pinning group that also have weights for other groups (such as for armature control), then all the weights are normalized, reducing the pinning weight based on the weights used in other vertex groups. While weight normalization for groups used for a specific purpose (such as armature control) is OK, if vertices are in groups that have other uses, such as pinning, those weights should not be normalized along with all other weights – it screws up the pinning of the cloth. Seems like the same might be true for soft-body Goal vertex groups.
Has anyone else noticed this, or found a workaround? It’s not really a bug (no actual dysfunction) but rather a fault in design, I think, but maybe should be reported as a bug since it can affect how the pinning of cloth objects works.