When script is running you only see when some of the commands are not successfull.
Is there a way to see which command are executed and to show the substitution of variables as every line is executed ?
set -x
for each level of the process, including each function() within the script...alternately, you could also echo script pre-interpolation via
set -v
assuming ksh or bash...
Actually, assuming a posix-compliant shell. set -x and set -v are both standardized 
Use the -v option of the cp command when copying files.
-v Cause cp to be verbose, showing files as they are copied.
Check in the man pages if the commands you use also support this option or a similar one.