Well I asked Humax for a progress report and got the following from the lady I have been dealing with there..
Is your Power Saving in Standby and Automatic Power Down OFF?
MENU – SETTINGS – SYSTEM – POWER MANAGEMENT
You will see above two options ON as a default.
Please turn them off.
Then, please turn the box off using rear switch and turn it back on.
As a IceTV user you need to have HDR-7500T to communicate with the IceTV server all the time.
When Power Saving in Standby is ON, when HDR-7500T goes into the standby, it goes into what we call ‘passive standby’.
It means none of USB ports, network, terrestrial etc will operate during standby mode.
(Only those require to wake up HDR-7500T at scheduled time which were stored before HDR-7500T was put into standby will run)
Therefore, if you have above options off it will not communicate to the server and you will lose some recordings you set up during HDR-7500T was under standby and paddings on some recordings.
We were carrying out investigations on paddings as many customers were claiming contrary opinions on paddings.
We have collected valid testing results from comprehensive testing with IceTV EPG on HDR-7500T and very close to put an end on the padding issue.
Until we have final confirmation I cannot say whether there is any permanent resolution on padding issue but there may not be a need of any resolutions.
I am a bit confussed by this, my topfield shuts down and only receives recordings when it comes on (to either be watched or record something else) I like that solution as it works fine as long as you record a few shows a week and understand the limitation. And if padding is set it automatically comes on early to apply the padding..
The solution from Humax is a power waste as they suggest the unit stays on 24/7....

EDIT:
This makes sense now, so what may be happening is you schedule a show for 8pm, if the unit is switched off (power saving standby) leading up to the show starting it won't come on until 8pm at which point it missing the lead-in paddnig and then must decide not to do lead-out too if it missed the in? BUT If you leave the unit on all the time (or it is on at the time the show is scheduled to start) it will see the show is meant to start in 10 mins and you have 10mins padding so it begins early (this is why we see inconsistant results)... This is the only way her explanation of how to resolve the issue makes sense to me, if so, this is NOT how other units work and really is a fault but they are going to try and avoid having to fix it by telling us all to leave our units on 24/7 in order to resolve it... The "may not be a need of any resolutions" comment worries me.. Humax, do not try and back out of fixing this, there is still definately a need for a resolution, no other unit I know of on the market requires you to disable power saving standby so that padding works....
P.S. Can others try testing this, I will test tonight..