Testing the same for the native 7z File Manager doesn't fail, so the issue seems to be with TC.
I don't know what triggers it - this is an Apache conf folder rather deep within a package, and unpacking that folder alone then 7zipping it doesn't trigger the error when re-unpacking.
What baffles me even more, it isn't consistant at all. Sometimes I only get 1 file in the unpacked folder, sometimes 2 or 3. But only when un7zipping the entire package does it unpack all files.
I would provide a link to the file here if it wasn't for the fact that it's 10½ MB, and a very beta package not really meant for public consumption at all yet. Drop [me a PM - edit scratch that] your user name here and I'll mail you a link to it for those who wants to test and can/wants to help out with this issue.
[edit] No, it wasn't just due to the missing file endings, it's more... random.
[edit 2] PM's here...
my bad, let me know here instead and I'll mail a link.
And oh-so-right you are. I have a 7-zip wcx it seems - must be problems with that. My bad. I had no idea that I had such a thing installed.