Tvheadend

Hi, I'm running TVHeadend 4.3.295 on Ubuntu 16.04.2 kernel 4.8.0-58 and LibreElec 80.02 on PI clients using 2 x DVB-T/T2 August DVB T210 v2 tuners.
I've noticed recently that tuning any channel is taking longer and longer, it's now around 10-15 seconds to get sound and video! a gull power down for around 30 seconds resolves it for a while, but it comes back after a day or so.

It looks like one of the tuners just crashes as the debug shows one failed tune event then one successful tune event.

I'm using the firmware files:-
dvb-demod-si2168-02.fw
dvb-demod-si2168-b40-01.fw
dvb-tuner-si2158-a20-01.fw

Any thoughts?

Dave