+7. Every once in a long while, the test
+
+ sage: set_random_seed()
+ sage: x = random_eja().random_element()
+ sage: x.is_invertible() == (x.det() != 0)
+
+ in eja_element.py returns False.
+
+8. The definition of product_on_basis() and the element constructor
+ for MatrixAlgebra are totally wrong. There's no reason to expect
+ a product of monomials to again be plus/minus a monomial.