Tvheadend

My tvheadend setup seems to work fine with recording as scheduled. However, I notice that after a few days, it "unsubscribes" to all the channels. I then miss my regularly scheduled recordings. I see that the recordings failed because of a "timeout". But when I check the current status of the channels I get "no data" for ALL of my channels. Here is one example:

2017-05-26 19:27:45.000 mpegts: 491.028MHz in Edmonton - tuning on Auvitek AU8522 QAM/8VSB Frontend : ATSC #0

2017-05-26 19:27:45.000 subscription: E7F3: "scan" subscribing to mux "491.028MHz", weight: 2, adapter: "Auvitek AU8522 QAM/8VSB Frontend : ATSC #0", network: "Edmonton", service: "Raw PID Subscription"

2017-05-26 19:27:46.204 linuxdvb: Auvitek AU8522 QAM/8VSB Frontend : ATSC #0 - poll TIMEOUT

2017-05-26 19:27:50.000 mpegts: 491.028MHz in Edmonton - scan no data, failed

2017-05-26 19:27:50.000 subscription: E7F3: "scan" unsubscribing

After I reboot the system, it picks up the channels again and recordings work fine.

I have this problem consistently. Recording only ever works for a few days. And it is like this with ALL the channels. It's almost like some sort of timer.

Anyone have any idea why it suddenly drops all the channels?

I am using tvheadend on Ubuntu 14.04 and my hardware is a Hauppauge 950 USB receiver.

Thanks!