I 'm going to hazard a guess that coming off a mix of DA's and levodopa - carbidopa based meds and going to levadopa - carbidopa based only might be responsible. Most of the leaflets that come with the meds for PD suggest that it may take up to a month to get things settled and the new norm is found. I dribble when asleep whilst not pleasant I seem to recall the experts don't appear too worried about it.
Stalevo contains entacapone which was described to me as a booster to get a better performance from the levodopa - carbidopa based meds.
There is a section on this website detailing most if not all of the PD meds, you might possibly find something useful in there.
Generally nothing happens as quick as we might wish for where PD is concerned.
There is also the helpline number if you want to know more.