NO

1 decompositions
 #0 -----------
   1: a(a(x)) -> b(c(x))
   2: b(b(x)) -> c(d(x))
   3: c(c(x)) -> d(d(d(x)))
   4: d(d(d(x))) -> a(c(x))

unjoinable peak
    a(b(c(x)))
*<- a(a(a(x))) ->*
    b(c(a(x)))