I am in the middle of switching my truck over to power boosted brakes. I got a brand-new booster/M.C. When I was bolting the linkage up to the booster push rod, I bumped the rod and it popped out of the booster. I pushed it back it and it locked in, but now it keeps popping back out. I mounted the booster to the truck and still have the same problem. Will this go away after filling with fluid and bleeding the system, or should I take the booster back? Anyone had this problem?

Thanks in advance!