Thanks for your replies!
I addressed the issue fo the good people of UVI, and this is the natural behaviour of the granular oscillators. With a grain size of say 500 ms, the fade in starts 250 ms before the position of the playhead, consequently delaying the sounds. Not a big issue, since it seems to be quite a few possible workarounds.
THANK YOU! Using modulation mappers for each LFO on/off works. I have currently assigned the possition knob to five LFOs with different shapes, and can switch between them using a single macro. So when the on/off button of for example LFO 3 is assigned to the macro, and the modmapper range 55-76 is set to 1, the macro turns the LFO on when it reaches the corresponding values, and turns it off when it reaches a point outside that range.
Again – thanks a lot!