If the same file is included in a tar archive (operation permitted in creation stage) then on extraction and error will occour and the operation will be aborted ignoring files that follows.

To reproduce:

/mnt # mkdir test1                                                              
/mnt # mkdir test2                                                              
/mnt # mkdir test3                                                              
/mnt # :> test1/file1                                                           
/mnt # :> test2/file2                                                           
/mnt # :> test3/file3                                                           
/mnt # tar cf comp.tar test1/ test2/ test1/ test3/                              
/mnt # mkdir decomp                                                             
/mnt # cd decomp/                                                               
/mnt/decomp # tar xf ../comp.tar                                                
tar: cannot remove old file test1: Is a directory                               
/mnt/decomp # ls                                                                
test1  test2                                                                    
/mnt/decomp # 

Tried and happens also on an old v1.00 ARM build.