Okay, the actual problem here is not the shlibs file, but upstream breaking API without bumping the SONAME of the library. I will raise this upstream, so we can find a way to deal with this issue for all distros and not just Debian (the result might be that we just always bump the version each time a new library is released).
Meanwhile, I think it's safe to let the package (and Tilix) migrate
back to testing.
Cheers,
Matthias
