The filename of the resulting file will be cut off after the first character without any warning.
While 7-Zip can handle paths longer than 259 chars when creating or unpacking tar files, TC cannot. Perhaps TC should support it as well. Right now, you sometime get no error, sometimes a cryptic error like when doing this:
Pack some files to a tgz file in this folder:
d:\123456789_123456789_123456789_123456789_123456789_\123456789_123456789_123456789_123456789_123456789_\123456789_123456789_123456789_123456789_123456789_\123456789_123456789_123456789_123456789_123456789_\123456789_123456789_123456789_123456789_123456789_\1\
You get this error:
Cannot modify TGZ files! Please open the TAR file inside the TGZ file, and add files to it instead.