let me show a little problem i've found in physics package (if it really is the problem in package), and especially in Bra, Ket, and in product operators

first

lets calculate a product of a projector and a Ket:

sum(Ket(Psi,s).Bra(Psi,s),s=-n..n).Ket(Psi,1)

in this case the result would be obviosly Ket(Psi,1) and it's true.

Let's modify it now:

sum(Ket(Psi,s+1).Bra(Psi,s),s=-n..n).Ket(Psi,1)