Scan transponder problem on 108.x images, please help

[vanbasten]

I've a problem with every 108.x img.
Dual feed environment, the scan only find about 700 channels on hotbird 13°, whilst if I use whatever 107 img the same operation find about 1600 channels.
It seems that some transponders have no sufficient signal, but the problem is just related to 108.x images (official e non)
I read something about a lnb tension to up, and I tried user configuration in satellite configuration menu, working on parameters, but nothing is changed.
Same problem if I load some settings, the loading is OK, but in fact many channels are not found.
IN case of loading settings, if I try to come to the transponder scan, I have a Fatal error like "Loading network failed".
Any idea? Any help could be appreciated, thank you very much in advance, ciao marco