TimeQuest and gate leve simulation incongruity

Thank you for your answer,

my evidence is:

1) the design is just a FF (no multicycle constraits). it has been simplified in order to isolate the problem)

2) after compilation, TQ says that Fmax = 130 MHz (my design runs @ F = 125 MHz and non violations are detected by TQ)

3) functional simulation (obviously) works perfectly

then: expected behaviour:

The output (q) is expected to follow the input (d) in a time within the launch edge and the latch edge

but: observed behaviour (in gate-level sim)

The output (q), sometimes (NOT always) follows the input (d) after the latch edge

Thank you