Tvheadend

I'm having a strange issue with encrypted channels, at first I thought it might be a signal quality/strength issue but now I'm not sure. I can tune FTA channels without issue, however when using the same hardware and software on encrypted channels i get continuity errors in TVH and playback is jittery and buffers. I can tune all FTA channel irrelevant of mux and several of these channels are spread across the range of MUX's on the satellite, and playback of encrypted channels on the same MUX is no good.

Tuner is a TechnoTrend S-1401 which uses the Philips SAA7146 chipset. TVHeadend server is running on Ubuntu 14.04 and has all the latest updates/patches installed. Client is OpenELEC 5.0 / Kodi 14 using VAPAU for playback. This tuner is natively supported by Ubuntu and I don't install any firmware or drivers to make it work. I also have the same problem with a Tevii S480, suggesting its not a hardware issue.

Any ideas?

These are the logs from TVH:

Jan 16 15:11:18.727 subscription: "192.168.1.69 [ XBMC Media Center ]" subscribing on "FOUR", weight: 150, adapter: "Philips TDA10086 DVB-S", network: "SKY Digital Satellite TV", mux: "SKY Digital Satellite TV: 12,456,000 kHz Horizontal (Default (Port 0, Universal LNB))", provider: "Freeview", service: "FOUR", quality: 100
Jan 16 15:11:55.061 subscription: "192.168.1.69 [ XBMC Media Center ]" unsubscribing from "FOUR" 
Jan 16 15:11:58.215 subscription: "192.168.1.69 [ XBMC Media Center ]" subscribing on "Living Channel", weight: 150, adapter: "Philips TDA10086 DVB-S", network: "Digital Satellite TV", mux: "Digital Satellite TV: 12,546,000 kHz Horizontal (Default (Port 0, Universal LNB))", provider: "Living Channel", service: "Living Channel", quality: 100
Jan 16 15:12:08.503 parser: transport stream MPEG2VIDEO, DTS discontinuity. DTS = 694800, last = 597600
Jan 16 15:12:08.651 parser: transport stream MPEG2AUDIO, DTS discontinuity. DTS = 639878, last = 518918
Jan 16 15:12:18.621 parser: transport stream MPEG2VIDEO, DTS discontinuity. DTS = 1587600, last = 1468800
Jan 16 15:12:18.687 parser: transport stream MPEG2AUDIO, DTS discontinuity. DTS = 1547078, last = 1426118
Jan 16 15:12:23.225 subscription: "192.168.1.69 [ XBMC Media Center ]" unsubscribing from "Living Channel" 
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It the above example FOUR is FTA and "Living Channel" is encrypted.