When running macdeployqt at post-link step, the paths of the libraries used by executable are not up to date (referencing Frameworks folder inside the bundle) therefore the executable is unable to find them.
See attached screenshot. The app was compiled with Qt 5.8 but macdeployqt was used from different versions of Qt (so don't take into account "(compatibility version 5.8.0, current version 5.8.0)").