50% regression (slower) in 95% KV | Observe latency (between builds 1774 and 1792)

Observed 50% regression in KV | Observe latency (95% PersistTo test) between build 4.0.0-1774 and 4.0.0-1792.
Still debugging which build this regression is introduced and what change(s) may cause the regression.

http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=ares_400-1774_95e_access&snapshot=ares_400-1792_1e4_access