I do think that some of the unipivots have fundamental issues, like chattering on the point, or some other instability. The Naim Aro is a good example of this.
I have ownd a Naim Aro for 25 ears along with a myriad of other arms. It is very stable due in part to the low centre of gravity ( below the pivot point ).
You either had a faulty arm or maybe it was your bouncy castle ( Linn ), though Martin Colloms used the Naim Aro on his Linn for many years and one of his key criteria in choosing the arm was its resistance to the problems of footfalls on his sprung wooden floor.