I'm going to go out on a limb here and guess that in one of the tumbler positions (rest, half-cock, or full-cock), the trigger "tightens up".
My Queen Anne is the same way. The trigger is very loose at rest. At half-cock, it is tight and barely moves, except a very slight side-to-side play, which requires some force to even notice. At full-cock it becomes slightly loose again, but nowhere near as bad as at rest.
If that's the way yours is, it actually isn't a trigger problem. It's a problem in the lock...specifically the design of the tumbler. The tumbler geometry prevents the sear bar from being at the same angle in each of the positions, preventing contact between the trigger bar and the sear arm in all but one position. I honestly think this improper geometry is inherent in all Pedersoli locks.
Even if your trigger isn't tight in any of the tumbler positions, this improper tumbler geometry is still a strong possibility, but may be compounded by the trigger not being positioned quite right in relationship to the sear bar.
For a much better explanation of the problem (and a description of how to fix it), check out page 84 in "The Gunsmith of Grenville County".