Mesh problem - part of mesh connect in wrong place

Of course, I tried on pants with one geom group and with more, same result but defect in different place. Here it is with one geom group:
Package

Sonia08 I used your advice, but it only changed place :'(

Ok, so I opened the blend and the right guess turned out to be, well, all 4 of them.
1). Type "bootcut" in the search bar and clone this item. Export the mesh. Append it in your scene and combine all of its meshgroups with Ctrl J;
2). Delete all vertex groups from your pants and re-transfer the weights;
3). Do this;
4). Delete the appended mesh and append the pants again, this time without joining them;
5). Use them as a reference in the process of splitting the mesh and adding cut numbers.
6). Delete the reference and replace the original blend in the cloned pants' package

Gradient should do. For the future, you can use Blur brush prior to removing vertex groups from certain areas. The point is to assign to vertices the right vertex group. Values do not matter, they will autonormalize after you remove the opposite group and click on Autonormalize.

For this type of meshes you have to use an avatar with lowered hands and assign weights differently. Explained here