Upload Bandwidth Issue Fortigate 60D

[RedRhombus]

I have a FG 60D running v5.2.13 firmware. We have just had a 20/20Mpbs fibre link installed and I am noticing that we are getting reduced uploads speeds, about 15-25% of what I would expect. I have followed the following troubleshooting steps which have resulted in several assumptions. Connected the ISP supplied Cisco 800 Series and confirmed that i get close enough to 20/20 speeds. This rules out the NTU and the WAN link. Connected directly to the LAN port on the Fortigate. The problem still exists with 19/4 speeds. This rules out the switches, cables and WAP's. Checked duplex settings on the Fortigate and connected NICs and confirmed all set to auto and negotiating correctly. This rules out a dupex problem although I was sure this would be the cause. Updated to the latest firmware. I have implemented the traffic shaping in accordance with the ISP's recommendations and tested to confirm the policies are applied. Remove all UTM features from policies and tested. Problem persists. Where it gets interesting is that if I configure the traffic shaping to 1000Kbps (up and down) and run a speed test I still see uploads at a significantly slower rate. In the above example it was around 0.95/0.2 Mbps. This to me would be an indication that it s now a performance problem with the FG. This issue may have been present since we have had the device as the previous WAN link was an ADSL service so the difference would have gone unnoticed. Any ideas? Does the ratio look familiar to anyone? Nick