Do you upload files from a remote network or from the local network?
The transfer speed can also be affected by the antivirus if real time scanning is enabled. Disable the antivirus temporarily to test.
These are some of the other factors that influence transfer speed:
- read/write speed of the disk
- network card speed (full duplex vs half duplex)
- cable speed or WiFi speed
- switch/router speed
- quality of service settings