tendencies and vector-smooth

Hello,

when using vector-smooth my tendencies start around 0.1 but end >0.2 (should be around 0.1 as well)

How can I prevent that?

(setf tend-list
'(0.1 0.4 0.2 0.6 0.5 0.5 0.9 0.7 0.7 1 0.9 1.2 0.9 0.9 0.5 0.5 0.6 0.2 0.2 0.1))

(list-plot
(setf dur-mults
(loop for i in durlens
with seed = (init-seed 123)
collect
(vector-smooth 0.3
(gen-tendency i tend-list :variance 0.2))))
:zero-based t :join-points t)

Thanks for help, Achim