The arbiter may take out GNT# at any time. A device that loses GNT# might complete its present transaction, but may well not start off just one (by asserting FRAME#) Unless of course it observes GNT# asserted the cycle prior to it commences. The ecu Facts Security Board provides recommendations https://nathanlabsadvisory.com/achieve-hitrust-compliance-in-the-usa-to-protect-sensitive-health-information/