Quick update and massive thanks to Antony at Lavatronics support for identifying the problem and replying so quickly. The problem appears to be bugged DVB module drivers, rolling back to an earlier driver should cure the problem.
Here is part of Antony's reply:
OK the problem itself is down to a small software bug in the latest dvb-modules drivers that were released which are a set of drivers that directly relate to the tuners, the bug being after a short while of zapping either softcam of CI will still appear as active but will no longer clear channels, this can be when being used with an official viewing card or by other means, makes no differce, the result is the same in that the channels will not clear. The powers that be are aware of the problem and have updated accordingly already but the issue can be with third party firmware which have either not updated their own firmware yet or still have the buggy dvb-modules in their update stream (you do and online update and end up with the bug being present).
There are various methods that you can use to roll back the dvb-modules drivers to those that work fine, it can depend on the type of firmware you use but usually it's rolling back to the 060712 dvb-modules driver that will do the trick.
Thanks again to Antony and Lavatronics and hopefully this will help anyone else experiencing the same issues.
