Gm54-120 wrote, "Im only guessing but it appears the anvil is backing out of the cup. Either the head spacing is off with the Fed209 or the primer pocket is not supporting that area on the primer very well."
One thing i would do is measure the primer length. Install the primer in the rifle, and close the bolt. Remove the primer without firing it. Measure the primer length again. Myself, i like to see the primer measure around 0.003" shorter after it has been in the rifle. This helps keep the anvil from walking out of the cup when fired.
Hopefully, the W209 primer will fall right out after being fired. If not, i wonder if trying a metric o-ring might be something to think about.