I can understand the possibility of sticking with the e-max and 120 gr. of BH. With BH (smokeless and progressive burning) the heavier the bullet the more efficient the powder is and it does create significantly more pressure and velocity. Which of course creates more back pressure on the nose of the 209 creating expansion and certainly possible to push the primer back up into the hammer hole in the bolt.

You also have indicated you have inserted a head spacing washer in the breech plug, so you probably have taken care of the more common reason for a primer being pushed into the bolt face.

I have zero experience shooting the e-max, but a lot of experience shooting 200 - 215 & 230 grain bullets. Even today with the Super Disc I experience some primer sticking in the stack of the breech plug (W209) even when the primer has not been shot. The current breech plug is a new plug and the only plug that I have that creates this problem. The next time I strip it to clean it I will mic the stack and probably run a .243 mill bit in it to open the stack just a touch. The heat treating process does cause the diameter of the stack to shrink from its processed diameter to the diameter it will be when completed. This plug I believe has tightened more than the norm.

Hope you get everything to work for you. Now that you head spaced your BP, have you thought about trying a regular CCI 209 primer versus the Mag primer? The pressure created by a Mag primer creates enough back pressure in itself to start the primer moving back especially when all that heat and pressure needs to get through a .032 flash hole in the vent liner. Mag primers are just tough on the BP and the vent liner.