I've just got back from an Internet-free week on Norfolk Island to see an email from Daniel Hall at IceTV saying that he's implemented the IceTV-side changes needed to fix the problem.
Corresponding changes need to be made on the Beyonwiz side, and I'll do that ASAP. When I'm satisfied with my own testing, I'll make patches available to IceTV and on the Beyonwiz forum to allow anyone else who wants to be on the bleeding edge to give it a go. I'll endeavour to make the patches compatible with both the latest official version and with the latest beta.
Like grumpy_geoff, I'm puzzled why Pauloz53 is seeing the problem on his T3, but not on his T4, since the issue that I think is the cause is common to all Beyonwiz T series models.
The "16 bit" reference that Colin (MD) made is to the fact that IceTV event ids are 47 bits, or more accurately, 13 decimal digits (IIRC), but the Beyonwiz T series can only store 16-bit event ids. That can cause two (or more, but that's fairly unlikely) distinct IceTV event ids to be mapped to the same Beyonwiz internal event id. Because of the way that the IceTV event ids are allocated, if collisions happen, they're likely to happen in runs, and so the missing parts of the EPG tend to be a run of several programs. For more information than you really wanted to know about the problem, see the Beyonwiz issue tracker item
Bug #603: Gaps in IceTV EPG. For even more excruciating detail, see
Gaps in IceTV EPG on the Beyonwiz forum.