Ubiquiti UAP AC LR: Slow ethernet port on LEDE 17.01.0

I have a Ubiquiti UAC AP LR running LEDE Reboot 17.01.0 r3205-59508e3. There's no firmware download for the LR model so I downloaded the UAP AC Lite firmware, which was easy to install and seems to run fine.

I noticed some slow speeds on Wifi clients so I ran some iperf3 tests between the Ubiquiti and my router (WRT1900ACS LEDE 17.01.0, r3205-59508e3) to test the ethernet port. The best speed I get is ~350 Mbit/sec from the Ubiquiti to the WRT1900ACS.

I've tested the ethernet cables and got 950 Mbit/sec between the WRT1900ACS and another computer (iperf3) for both cables.

As far as I can work out the problem could be:

  1. Slow CPU on the Ubiquiti;
  2. Bad LAN port on the Ubiquiti;
  3. LEDE configuration problem;
  4. Driver problem in LEDE (maybe b/c it's for UAP AC Lite, not UAP AC LR?);
  5. Problem with the PoE adaptor.

I didn't run iperf3 on the stock Ubiquiti FW to rule out 3 & 4.

I'd appreciate some help troubleshooting this, if anyone has any suggestions.

I'm pasting /etc/config/network from the Ubiquiti AP and my "best" iperf3
result at the bottom.

Thanks for reading!

/etc/config/network

config interface 'loopback'
    option ifname 'lo'
    option proto 'static'
    option ipaddr '127.0.0.1'
    option netmask '255.0.0.0'

config globals 'globals'
    option ula_prefix 'fdf2:7a26:c632::/48'

config interface 'lan'
    option type 'bridge'
    option ifname 'eth0'
    option _orig_ifname 'eth0 radio0.network1 radio1.network1'
    option _orig_bridge 'true'
    option proto 'dhcp'

iperf3 WRT1900ACS -> Ubiquiti

-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Accepted connection from 192.168.1.100, port 52436
[  5] local 192.168.1.101 port 5201 connected to 192.168.1.100 port 52438
[ ID] Interval           Transfer     Bandwidth
[  5]   0.00-1.00   sec  39.0 MBytes   327 Mbits/sec                  
[  5]   1.00-2.01   sec  42.8 MBytes   357 Mbits/sec                  
[  5]   2.01-3.00   sec  43.1 MBytes   363 Mbits/sec                  
[  5]   3.00-4.00   sec  42.8 MBytes   359 Mbits/sec                  
[  5]   4.00-5.00   sec  43.2 MBytes   361 Mbits/sec                  
[  5]   5.00-6.00   sec  43.1 MBytes   362 Mbits/sec                  
[  5]   6.00-7.00   sec  43.0 MBytes   362 Mbits/sec                  
[  5]   7.00-8.00   sec  43.1 MBytes   361 Mbits/sec                  
[  5]   8.00-9.00   sec  43.1 MBytes   362 Mbits/sec                  
[  5]   9.00-10.00  sec  42.9 MBytes   359 Mbits/sec                  
[  5]  10.00-10.01  sec   128 KBytes   208 Mbits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth
[  5]   0.00-10.01  sec  0.00 Bytes  0.00 bits/sec                  sender
[  5]   0.00-10.01  sec   426 MBytes   357 Mbits/sec                  receiver