Post DSO, I also tried removing unwanted channels, took it down to about 12TV and no radio. For me it had some benefit, but still not great. In addition, my EPG wouldn't go beyond 3 days ahead, however long you left it.
I don't know if it is still the case, but channels in the range 800 have historically been blamed for recording problems. These channels mean that auto tuning has managed to pick up stations from more than one transmitter. As a result, I always use manual tuning. This isn't as bad as it sounds, you just need to know the channel numbers of the 6 multiplexes on your local transmitter; there are 10 to 20 stations per multiplex and they are sorted automatically.
Go here http://www.digitaluk.co.uk/postcodechecker/ put in your details and tick the "trade aerial installer". The results page will show you possible transmitters and the probabilities of receiving. Look at the "Coverage Prediction" for "Now" for the 6 multiplexes.
For a near Emley Moor (HD80LF, 12, Trade)...
http://www.digitaluk.co.uk/postcodechecker/main/trade/HD8+0LF++/12/0/NA
The results page shows multiplexes 52, 40, 46, 43, 50, 49. You will probably find that 43 won't actually give you any new stations. Note that to do this you would have to delete your existing channels first and this would clear your recording schedule.
As for 23...
These recording failures are something different from anything that I have seen in the past. I have only had 3 instances, so not a lot to go on, but in each case the programme was marked in the EPG and listed in the schedule, just changing the channel caused the recording to start. I just don't have enough to go on to add anything more helpful.
It has to be said, that running 21 after DSO made my 9200 impossible at times with it taking 40 seconds to respond to commands and often freezing completely. I often dare not watch anything while recording for fear of the freeze wrecking the recording. Compared to that 23 is a huge improvement, I just wish that this little problem wasn't there instead.
The forums show a number of people who have not experienced any problems with 23, only time will tell.
AlanB, June 2010