So much depends on functionality in any add on on an unstable platform. Due to Laminar's "official" advice to developers, and some developers totally ignoring this advice, other plug ins made by said developers could be interfering with plug in driven aircraft, such as the DC-3 and Saab. Because of this, it would be impossible to diagnose the problem/s you are having. I haven't had many reports of problems with the DC-3 in XP11 (3 actually, including this one with the engines), so my GUESS is that something is interfering with them.
I have 2 suggestions you could try:
In the order given...
1. Load the DC3 in Planemaker again, go to File/Save. Make sure you save it. If that fails, try 2.
2. Load the DC3 in a clean install of X Plane (or one that has no other plug ins running, except for Gizmo.). Don't just disable them. Remove them completely from your X Plane folder. Don't delete them. You'll need to put them back. Then load the DC3 and see if that fixes it.
Failing those two, I'm afraid I'm going to have to ask that you wait until X-Plane becomes final.