..."Hold sensitive", then yes, to an extent they are. Not as bad as some other rifles (the RWS34 and B26 come to mind), but not nearly as insensitive to hold as a pnematic or CO2 gun.
There's really no such thing as the spring "bedding in". A new spring takes a "set" the first time it is cocked, and might shrink a little bit more over time. But there's nothing that will change so radically from one shot to the next that the POI changes like that - and then changes back again.
Out of a reasonably healthy Gamo, a pellet will drop on the order of 2" on the way to a target 28 yards away. In order for the pellet to drop an additional 1.5", the velocity has to be on the order of about 250fps slower. That's a big drop! Virtually the only thing that will cause that sort of wild fluctuation from one shot to the next is dieseling... and if the rifle was dieseling that much, I think you'd both hear it and smell it.
