Bor full/sentry node stops importing new blocks indefinitely — internal "veblop producer stall" fires but never recovers, reproduces on v2.9.0 and v2.9.1-beta2

Bor full/sentry node stops importing new blocks indefinitely — internal "veblop producer stall" fires but never recovers, reproduces on v2.9.0 and v2.9.1-beta2 #154