Tvheadend

Hi,

I used to have tvheadend installed on a Mitac Pluto server.
It was working fine but for a random of time. At a point, the hauppauge nova-t stick got disconnected from the bus and I had to kill tvheadend, unplug and plug back the stick to make it works again. I suspected a power management of the USB3 on the Pluto. Tried to disable the power saving but with no luck.

So I moved to a raspberry pi 2 solution and wanted to install tvheadend on the rasp. I am using the Openelec distro and the installation was smooth.
Problem happened at the mux scanning.
I am using the muxes discovered on the Pluto but for only 1 mux I got scan result ok. For all other I got a faillure.
Result is I am getting only 4 channels out of the 23 available.

Looking at the signal strength on both server (Pluto and Rasp), I see there are lots of errors reported on the rasp. On the Pluto, signal quiality is 100% and strength is about 75%

Would the problem be with the rasp? lacking power may be for the nova-t stick? But I am using the official 2 amp DC adaptor.
Or is there a tweak possible on tvheadend 4.0 to increase the gain maybe to get better signal?

Thanks.