Please try using FTP to upload the data. Slower connections can sometimes be interrupted when using other methods. With FTP, even if interrupted, the transfer can be resumed and confirmed to be complete once done.
Support FAQ: https://galaxyproject.org/support
- Loading Data https://galaxyproject.org/support/loading-data/
- FTP Upload https://galaxyproject.org/ftp-upload/
Thanks! Jen, Galaxy team