Look at local vs global density, what is the problem "box"? Local density might have local fixes, global means you've got a bigger problem if violating max. Like picking a foundry flow that won't let you pack poly the way you pack active.
My only look at fin stuff showed poly prepatterned and taken away by block features, how is that able to violate max density? And where? Are you making yet another general question out of little "oopses"?
Maybe if you showed the region and the error markers
something would suggest itself to somebody. Other
than that, look to any poly that could be removed
without affecting function. Maybe there's "leftovers"
that could be cleaned, since (IME) the fins start off
"all-in" and you have to take away, maybe missed
some or quit at "passes LVS".