F300-25 extremely slow data despite link test stating otherwise

Hey all,

I have a Force300-25 (well a 4pk but this is unit two, #1 wouldnt connect at all and yes I will be opening a support ticket once I am done testing it) connecting to a 3000L (AP) that also has 15 Force200's and Force180's on it. The AP is working normally (well client shedding aside) but this one new radio though it connects and the link tests show the bandwith is there I am getting dialup speeds in both directions. RF signal is lower than what we like but still within tolerences and the radio runs in DS3 both ways, so the required bandwidth is there. Spectrum scan shows my local with no interferers.

None of the other N based SMs is experiencing this, this is the only AC based radio on this AP. The AP is running 4.5 (both banks) and the SM came with 4.3.1 but was updated to 4.5, then downgraded in testing to 4.3.1 which did nothing to help and back to 4.5. 

I use this same basic config (minor differences changed by radius) on all clients except a few that required a different setup.

The SM config is:

Radio: SM/tdd

QOS: set to max/traffic priority is off (normally we have this on but in testing we turned it off)
System: set device name, ntp server, cnmaestro settings, syslog ip and disabled unused login accounts

Network: NAT, PPPoE auto, port security off, ethernet ip and dhcp server, management ip and vlan, data vlan, Ethernet port: only smart speed is disabled, all else is default, PPPoE enabled, configured (connects). under advanced usually only nat helper for sip and dhcp option 66 are enabled but currently all is disabled, DMZ disabled,

Security: set to only use wpa2 (usually we use both wpa2 and radius, but we are diagnosing this unit so radius is disabled), preshared key is correct (we do connect to the AP), Radius config is currently default, firewalls are both disabled.

SO any ideas? this ones got me stumped!