Had the issue on my QNAP nas with 2.0.105 too. Your way worked and saved me a lot of data copying! The only difference being that I did not shut down the computer, but quit the app on computer one (mac) and switched off the app on the qnap in the app center.
I got the same issue on a QNAP TS-259 PRO+ with version 4.1.0.. However, I initially downloaded the i386 version, and later retried with the linux i386(glibc 2.3) version which did not give me this error (and could start). # uname -a Linux NAS 3.4.6 #1 SMP Thu Jun 12 03:34:00 CST 2014 i686 unknown