LGRP = layout groundrule package. You should have a
controlled ("blessed") document that says in plain text
(with pics) what each rule is.
So pick one flagged error and measure. Does, or does it
not, agree with the document? With the error report?
Secondary files such as your local, or foundry "golden"
DRC, should match the document. There has to be a
discrepancy somewhere between the four points
(document, layout, Encounter, foundry deck) and it's
on you to figure out which, and push back or fix layout
appropriately.
I guess there's another possibility here, that the
layout synthesis rules are the problem (and the Encounter
deck might match, but both mismatch the foundry checks).
At some point you have to take off your necktie and
crawl in the mud. The time is now.