I have had this experience also. Scrum causes a crunch at the end. This provides focus which is good for projects but it also leads to overtime and quality problems and it doesnt allow time for the product owner to test the story before the sprint review. Its also common practice for offshore teams in developing countries to give the client nothing until the sprint review and then to insist that it all be approved in 30 mins. This is terrible. But if you move to Kanban you lose focus on what your doing - the teams work becomes a whole lot of independent bits that arent integrated. So the best solution is Scrum and Kanban together with a high tolerance for slippage. Once you have done ScrumBan you wont go back to plain Scrum.