Dear Maintainer,
I, too, am seeing the same issue. Building the package myself
yields the same problem.
The problem is that the package's source code is being
improperly fetched from the GitHub repo. The repo relies on Git LFS
(Large File Support). This feature must be explicitly configured by the
fetching client via `git lfs install`, which makes modest changes to
`$HOME/.gitconfig`. If this is not done, then the icon files will be
"pointer files" containing the metadata to fetch the file (URL +
SHA256), not the file data itself. This was clearly not done when
building `spnavcfg_1.2.orig.tar.gz`, resulting in invalid icon files.
After enabling Git LFS, I was able to build a working copy as
follows:
```
$ mkdir work && cd work
$ sudo apt build-dep spnavcfg
$ apt-get source spnavcfg
$ git clone git@github.com:FreeSpacenav/spnavcfg.git spnavcfg-git
$ cp -av spnavcfg-1.2/debian spnavcfg-git
$ cd spnavcfg-git
$ debuild -b -uc -us
```
The resulting binary then correctly launches and connects with
`spacenavd`. Hope this helps.
Schwab