Delay Degradation vs Glitch Peak Criteria for Constraint Measurement in Cadence Liberate

Hi,

This question is related to the constraint measurement criteria used by the Liberate inside view. I am trying to characterize a specific D flip-flop for low voltage operation (0.6V) using Cadence Liberate (V16). 

When the "define_arcs" are not explicitly specified in the settings for the circuit (but the input/outputs are indeed correct in define_cell), the inside view seems to probe an internal node (i.e. master latch output)  for constraint measurements instead of the Q output of the flip flop. So to force the tool to probe Q output I added following coder in constraint arcs :

# constraint arcs from CK => D
define_arc \
-type hold \
-vector {RRx} \
-related_pin CP \
-pin D \
-probe Q \
DFFXXX

define_arc \
-type hold \
-vector {RFx} \
-related_pin CP \
-pin D \
-probe Q \
DFFXXX

define_arc \
-type setup \
-vector {RRx} \
-related_pin CP \
-pin D \
-probe Q \
DFFXXX

define_arc \
-type setup \
-vector {RFx} \
-related_pin CP \
-pin D \
-probe Q \
DFFXXX

with -probe Q liberate identifies Q as the output, but uses Glitch-Peak criteria instead of delay degradation method. So what could be the exact reason for this unintended behavior ? In my external (spectre) spice simulation, the Flip-Flop works well and it does not show any issues in the output delay degradation when the input sweeps.

Thanks

Anuradha