5nS delay just from the interconnect? I have never seen
that kind of loading in logic. Perhaps it's just a terribly
bad routing, or perhaps the line capacitance is mis-
extracted or mis-transcribed?
It is unclear where the next registered stage is, in this
circuit. Delay > period is going to be a timing hazard
that depends on PVT (expect low temp fast, to be OK
and high temp, slow, not - so your circuit would be
"environmentally unreliable" in its behavior. Skip a
cycle or catch bad data starting somewhere in the
middle.
I'd look at the timing model and input validity first,
and see what accounts for the ridiculous loading.