@alex_malyu I re-read and you are right. I was sure that only the main expansion file was downloaded and that the patch file download had to be initiated by the app, but this is not the case. At least for now a work around is using two files, but I might get the same problem when the app expands.
I am using Windows 7 64-bit and have tried MinGW 4.9.2 compiler on Qt 5.5, MinGW 4.9 on Qt 5.4.2 and MinGW 4.8 on 5.3. I also tried MSVC2012 on Qt 5.5.
I will try post a bug report and see if someone can reproduce the same.