I am wondering if you are aware of
using LinearAlgebra
(vals, vecs) = eigen(Symmetric(K))
That’s very clever of you! Note, however, that this a bug in a package that is not part of the language per se. Bugs happen, and that does not reflect on what Julia is or isn’t able to do. Also, while I am as much of a fan as drama as the next person, it is unlikely to lead to the timelier resolution of bugs.