You may have a primary extraction issue. A shim inserted between your bolt handle ramp (on the side opposite the bolt handle) and the rear baffle might help you pull the brass loose.

If it were me, I'd probably push a wooden dowel down the barrel and bang on it with a hammer once I knew the bolt was lifted all the way up.
What Thomae was telling you to do is close the bolt. Place a shim between the rear of the action and the rear baffle. When you lift the bolt up the tolerence or slack is taken up and the ramp on the bolt will utilize the ramp on the rear baffle more effectively, possibly moving the case enough(primary extraction) to be able to open the bolt.

If that does not help making sure the bolt is open all of the way you could either use a dowel rod or a cleaning rod and insert it through the muzzle very carefully and tap on the end to push the cartridge back. A light taping on the bolthandle in the opening direction is anothr thing to try. Remember anytime you use a hammer it is with care and thought.