No, that is not normal.
It should be safe to gently pull off the space bar and look inside. If you have a key cap puller, pull each end gently and then the centre. Otherwise, you could use a flat-head screwdriver, but then you would have to be more careful to not damage the key. If you use a screwdriver, hold your other hand on the other side of the key to prevent warping it.
Now, to the left and to the right there should be a black cross-shaped stabilizer stem that should fit inside a cross-shaped hole mount under the space bar. The two stems don't have any springs in them, so they should have fallen to the bottom.
- Does anything look like it is broken?
- Do the stems and hole mounts match up? Newer Leopolds have been reported to have the mounts in different places than other keyboards, including older Leopolds. It looks to me as if the space bar is not the one that came with the keyboard originally, so I think that this is a possibility.
- If you pull on one of the cross-shaped stabilizer mounts with a tweezer or pliers, does the other one come along?
If none of the above, it may be that the mounts are just a little loose. Put a tiny piece of sticky tape on the sides of the left stabilizer mount and try if it works better.
Edit: Bah. Lots of replies while I was writing the above. Let's hope that you can fix it with a bit of sticky tape.
