I'm on satellite : Astra 1 + 3 (TV-Vlaanderen -Flemish/Dutch channels + German channels) + Astra 2 (English channels). As I already have said, EPG grabbing works without problems if "idle grabbing" is selected. The problem is starting EPG grabbing by PowerScheduler++ in case "idle EPG grabbing" is OFF. So, there is probably an EPG grabbing bug. I suppose so. Thanks for the tip to uncheck the option "store date only for selected channels". But if I understand this correct, in this case the EPG will be grabbed for ALL channels. This is not needed and it will take even more time to grab the wanted EPG information for some channels. I will do a final test with "store date ..." off + idle epg off and let start EPG by PowerScheduler++. PowerScheduller++ is supposed to do so this night at 3 o'clock. Tomorrow I can tell more.
The reason I've had to do it like this is because if I tick more than one channel, it grabs on the first one, which gives the EPG data for all channels, then grabs on the second one, grabbing the same data again and so on, which was making the grabbing take ages and by the time it had finished, it had reached the interval time and would start all over again So I have to tick only one channel and then untick "Store only" so that it keeps all the data it's grabbed on the one pass for all the channels. This may well be a peculiarity of UK DVB-T Freeview though and this bug may not affect you.
I'm not sure how the PS++ grabbing options work but maybe they're just designed to allow you to set a time to wake the PC to grab and it still requires the idle EPG grabbing to be enabled as Lightning303 suggests.