This sounds like its more related to the way that eventide units in general work. When you load up a preset it is essentially completely changing the box as the algorithm is being loaded. So if you had an effect with delay then switched to a different one it will cut the previous effect short as it loads the new algorithm. Setting to DSP+Effect works fine when bypassing but if you want to change the effect it will cut it short. At least thats how it works in the harmonizers.
Cheers
