My suggestion is just a guess from the error message. It seems there is a lot of trial and error to find what works. I have only built one package since the rpm change and it seemed to work just fine, but it only have one zipped source file, so I don't know.
You can find out very quickly, just by zipping just the next file, and checking to see if the build fails at the same step, or continues and fails on the next file. If it fails on the same spot, then zipping the files will not likely be the solution.