Step one is to have Product/Sales define an SLO for support ticket resolution (and for all your key services, if you haven't already). Give more sprint time to

Step one is to have Product/Sales define an SLO for support ticket resolution (and for all your key services, if you haven't already). Give more sprint time to whatever's falling behind. If both are falling behind, you need to slow down the velocity of which you're demanding features be shipped, or loosen the SLOs, or hire more programmers.