Tvheadend

I have a very strange issue with my USB tuners that I am hoping some on can help me solve.

Setup:
Odoid XU-4 (like a raspberry but much more powerful)
2 GB ram
Has 2 * USB-3 ports.
1 * USB-2 port.
2 Tb USB HDD attatched to USB-3 port.
USB-3 hub (4-port) attached to one of the USB-3 ports.
2 x Kworld USB DVB-T DIGITAL TV TUNER Stick II (DVB-T395UR) - Uses the AF9015 kernel module
Single cable that is split into 2 outputs just before the tuners
Both tuners have 97-100% signal strength.
Ubuntu 15.10
Tvheadend 4.0.8 (from tvheadend raspberry pi repository)

Tests done with HDD plugged in and unplugged.

So the problem that I am having is that if I plug just one of the tuners into the USB hub, I can record perfectly with no continuity errors, however when the second one I plugged in, even though the signal strength is good, I get thousands of continuity errors. This always happens to the 2nd tuner to be plugged in, even if I tell tvheadend not to use the first tuner at all. I have even given the system a day of sitting on and idle just to make sure that no other scans are going on.

Another test that I have done with the same result was to remove the USB-3 hub.
I also tried connecting 1 tuner directly to the USB-3 port and the other tuner to the USB-2 port

Anyone have an idea as to what might be causing this?