A couple of things:
First, look to make sure when you move the mag attachment button on top, that the prongs move on the inside face of the mag where it attaches to the camera.
In the future, try to avoid snapping the mag onto the body rather than moving the attachment button back, attaching the mag and then releasing the button.
As David Odess points out in his FAQ section:
"How can I use my thumb to save my feet?
When you put a magazine on a Hasselblad body, don't "snap" the top of the magazine on to the body. This creates a lot of pressure on the two feet on the bottom of the body, and will eventually cause the feet to bend. Instead, push the button on the top of the magazine over with your thumb before attaching the magazine to the body." http://www.david-odess.com/faq.html#q16
If either of those don't seem to help. As has been suggested, get it CLA'd. Dave charges $95 bucks I think, to go through a mag and restore it if it can be restored. In using his services for years I've found he's worth it and as good as sending it to Hassie for factory service because he used to work for them before setting out on his own.
And if your CM's feet are bent, the last thing I would try to do is straighten them out by myself. If they're not properly aligned and/or if the springs are damaged, you may cause more problems than just sending it to a qualified tech.