vp.play(interp = 2) strangeness / click

[Sciss]

In workspace WegC_170507 patch QBO cluster v3; 18 to 24 km, -165W 2.5N, full time series; if I change

val vp0      = vr.play(tp, interp = 1)
val vp       = Ramp.ar(vp0, speed.reciprocal)

to

val vp       = vr.play(tp, interp = 2)

One can hear a click at around 70% elapsed. I have no explanation other than that the UGen graph expansion expands differently when using interp = 2 (which is well possible), and that this one type of expansion has a problem.