Peak level change when grouping channel

So I have a bass sample which is peaking at 4.6 on a single channel, I then run it through a group channel, fader set to 0 dbs, no plugins on each, and this channel is reading 7.7 dbs. I have just upgraded to cubase 8 and this did not happen on cubase 6. I just don’t understand why it is changing when nothing is there to change it.

Any help would be great, thanks