The AD8561 model in LTSPICE 17.1.15 appears to have the output and the complementary output mapped the wrong way round. The outputs go high when they should go low and vice versa. Response to a triangle wave shown below, n001 is the output pin. I noticed this has been raised before ( https://ez.analog.com/design-tools-and-calculators/ltspice/f/q-a/566887/ltspice-ad8561-macromodel-symbol), just letting you guys know the problem is ongoing.