This is where it gets ugly. The tabs that hold the valve assembly in are VERY tough to straighten because of the thickness of the material, the limited amount of leverage you can get on them and the fact that they are long and curved.

Undoubtedly when these were manufactured the copper was dead soft but when formed it work-hardened which is fine until you try to work with it later. The work hardening occurs at exactly the points that you need to bend causing the adjacent areas to bend first compounding your efforts to get the tabs straight and lined up with the slot.

Annealing would probably make the whole process easier but you'll have to dig the seal out and rig some sort of heating device to keep the heat away from the solder joints, or ideally build a fixture for soldering the tube back together.

As you can see by the scarring around the slots, I wound up distorting that part getting mine out, but it's easy to straighten with a small hammer and dolly. No harm done.

Be prepared to have your patience tested here.