Upload problem

Hi,
We have encountered a problem.One of our customer who has a line to the Internet 8/4Mbit we put RB450 with version 4.11. All looks like good, just the upload the direction to the Internet does not exceed more then about 500kbit (one connection). When I connect the PC directly to the cable from the internet I reach full speed (4Mbit). The RB450 is not any set Queues, FW, Mangle..etc. conntrack is on. WAN is connected to port 1 and LAN port on the 5th. No bridge created.
We have the same problem with x86 (4.11) with the internet connections about 40Mbit FD. Here the uplaod does not exceed about 6Mbit.
Any idea pls?

name="WAN" mtu=1500 l2mtu=1526 mac-address=00:0C:42:82:EA:DD arp=enabled 
      auto-negotiation=yes full-duplex=yes speed=100Mbps



name="LAN" mtu=1500 l2mtu=1524 mac-address=00:0C:42:82:EA:E1 
      arp=enabled auto-negotiation=yes full-duplex=yes speed=100Mbps 
      master-port=none bandwidth=unlimited/unlimited switch=switch1

I apologize for my English..