Tobias,
Pipeline's approach is an approach for individual Realtracks and Supermidi tracks (at least as I presently understand it).
With this in mind, I tried soloing each of the tracks and it seems that the holds on the two midi Supertracks are fine. From what I can tell, it's Realtrack #1814 (Guitar, Acoustic, Fingerpicking CelticAir Ev 085) that has the loud hold. This means that Pipeline's approach should be able to be used by selecting that single Realtrack and it will solve the problem.
Below is an alternative global approach that might also be worth investigating....
1. Enter into Realtrack preferences (#1 on the image).
2. Enter a negative value in the "Adj. Shot Velocity" window. (-2 or -3 seems to be a reasonable value)

Let us know how things went for you.
Regards,
Noel