When transferring the skin weights, select Lateral Positioning. You will see nodes in the inseam that are assigned the wrong color. Select one of the nodes with the wrong color and click the Selection Tool expand button (diagonal up arrow) to expand the selection as needed. Then select the Right or Left button to correct the node assignment. Note: The buttons are for the character's right and left. Repeat until the nodes are corrected.
When you get the nodes corrected, click apply.
Try to do this the first time you transfer skin weights, with the character in an A position. You can correct it after the object is messed up but it is harder to get the nodes selected.