Yup! I pulled one apart (and reassembled it) to see what the problem was reloading, and even with actually using the things.
I now understand why the film has a double hump on the tongue unlike regular film with a one sided or pointy tongue. It's to do with the guiding coils inside the cassette. Put a rounded or pointy end in and it will easily jam up in the take-up cassette. Each hump is centered over the sprocket holes and the dip is in the middle of the film, between them.
One clever fellow I know actually adapted a cart from (IIRC) an Actrix? cass. He said something about a disposable camera cassette, anyway.
I got mine with an other regular Silette from a bloke who's Dad had died and left all his photo gear. When I say 'all' there was a folding brownie in a most elegant home-brew box so that it never got folded and as a consequence the bellows are just fine. The other Silette Rapid I is a manual adjustable model with a 2.8 lens and several speeds.
There were rapid films unused and some ordinary 12 shot films waiting to be loaded, I think. Yhat is how I knew something special was needed in the way the film was transported across the gate. Even a 120 to roll for the 620 Brownie, which has some spare reels.
The automatic Isomat (square) camera is rather basic but the lens is allegedly not too bad for a triplet. I have used it just to see if it goes and of course with nothing much to go wrong it is still very functional and pristine. The shutter release is kinda 'clunky'. With that and its lightness you have to be specially careful to hold it steady. There is no battery so it uses a selenium photo-cell. Not the best thing in the world.
Hey! It was fee!
Murray