Bill,
I probably posted this before on another thread- but all drums won't fit/work with all lugers.
Sometimes the magazine part of the drum won't even slide into the frame- but that is usually with earlier pistols.
I expect you can find the "high" spots, put a little black magic marker on the feed lips and on the bottom of the bolt, I'd take the hold open out- so it is eliminated from the equation entirely.
Then cycle the toggle by hand. I've found that without the recoil of a fired round- one frequently has to shake or slap the drum to get the rounds to move under the spring pressure.
The actual recoil is a necessary part of the operation of the drum, at least it is with all I have.
Hope this helps. But do try at least two lugers, or four.
I forgot, also after you insert the luger and it clicks in, pull back down on the drum to seat it firmly against the mag catch, there is often a little movement there- and you need to get it back down on the latch surface- this is especially important if the drum is a tight fit in the grip.
You did take it apart and clean all the grease out that GT left in and then put in some silicone spray or liquid lube?
I find the lube is important and like the "Dupont" silicone in the blue label bottle- but any thin oil is ok. There is a tremendous amount of friction between the cartridges and the drum surfaces- but it will get better with use.