QNAP keeps a list of installed packages in /etc/config/qpkg.conf . Sometimes you have to manually remove the entries for an uninstall app from this file to ensure it is completely removed. Look for Xeams in this file and remove it if you have already uninstalled it.

Also, ensure files are removed from /share/CACHEDEV1_DATA/.qpkg/Xeams and then reinstall.