Scott - sorry for the frustration - I know one of our support fellows was helping with this but I took a look and I can give you some answers but possibly not complete at this stage.
1) Unfortunately your site is in a region of latitude where we found a killer bug, and the geographic transformations don't work properly. Fortunately, this has been fixed in Pro 2.7.2 - could you download and install the new version?
2) Your drone is reporting incorrect altitudes. This is pretty common, and I'm unclear why it happens so much. (Most) Drones report altitude as ellipsoidal height from GPS since they don't know where the ground is, nor sea level. The terrain at your site shows ellipsoidal height of ~790 meters, but your metafile shows minimum altitudes ~690. (I assume you weren't 100 meters underground). See the attached - I've made a guess that the records showing 690 were when the drone landed, so I added 100 meters to your Z values.
The attached file MIGHT work, but this Z error does not explain why something is crashing.
3) can you clarify what is crashing? Here you say the Video Multiplexer tool, but your post on the webinar page said "ArcGIS FMV is crashing". Is it the whole program, crashing when you load the multiplexed video? or is the tool crashing and you're not getting an output video file? I tried your metafile with my own video, and it worked except for showing the drone underground. When I added 100 meters, it worked to bring the drone above ground and nothing is crashing.
It's possible your crashing problem is due to an additional conflict somewhere - but could you try my modified metadata file?
4) I try not to "pass the buck" but it could be something in your video file. If it still crashes with my metafile, could you try downloading this video file and using it in the multiplexer?
http://s3.amazonaws.com/ImageManagementWorkflowsTeam/FMV/multiplexer.sample/GOPro0037.mp4
If it works, then that would point to something wrong in your video file.
Hoping this helps - let us know.
Cody Benkelman