Hi, we have got a ISR4331/K9 with IOS XE 15.5(3)S4b showing the same log:
Oct 15 13:54:01.714: %IOSXE-3-PLATFORM: SIP1: cpp_cp: QFP:0.0 Thread:000 TS:00001842578982784425 %IPSEC-3-REPLAY_ERROR: IPSec SA receives anti-replay error, DP Handle 28, src...