The demos that won't load are lost causes unfortunately.
However, for future recording here's what you want to do
Copy this code onto your clip board
demorecording::startrecording( )
As soon as you join a game, hit both the "ctrl" key and the "~"(the wierd 1 under the esc key") key at the same time.
Once you do that, click the white box on the bottom(the one where you can type stuff) and paste the code thing. If you don't know already, "ctrl" + the v key pastes things.
Once you paste it, hit enter and then hit the same two keys you used to get into the console commands to get out of them.
To stop the demo, just leave the game and then you can go and view the demo. Best way to find out which demo is which is to go into your recordings folder and right clicking each demo and going into properties.
live/legions/data/recordings
^thats the path(or w.e its called) to get to the demos.
However, if you want to record another demo, you have to close out legions(not the launcher, only legions) and re open it and do the same process again to record demos.