299d3 4364-1 Code intermittent DEF ISSUES

Hello, I am looking for some advice fighting a event code on a 2020 299D3XE BX901013. My symptoms are no active codes during warm up and normal run time, after about 45 minutes of running a mulching head the 4364-1 (Aftertreatment #1 SCR Catalyst Conversion Efficiently Low Most severe (3)) comes up. I have Sis/ET and have followed the troubleshooting procedure SMCS-191N-035 with no smoking gun. Per the procedure here are my results: -No other codes active only 4364-1 after 45 minutes to 1 hour, then it clears after shut down. -Confirmed sensors are in the correct locations Grey on top (Post) Black on bottom (Pre), 12 volts at both sensor harnesses -Def quality is good per cat test kit and 2 gallons of fresh recently added, changed def and filter to be sure. -No visual leaks or kinks in DEF Lines -Def Dosing system verification test in ET successful pump cycles (New filter) -Def nozzle has no signs of crystals on the tip -Aftertreatment SCR System dosing test in ET OK nozzle appears to be spraying ok and produces 100ML (Spec 90-110 ML). I noticed while monitoring and during a manual regen the NOX sensors only read zero PPM most of the time. I have seen the pre sensor read 350ish PPM during a regen while it was dosing but that's it. I'm hoping some of the above Tier 4 experts can weigh in here, is this normal? *update on this i was able to plug into another 299d3 and its nox sensors read similar (0 most of the time)* DEF injector wire harness pigtail replaced per the service bulletin with 437-1451 wire kit (no signs of corrosion when stripping old harness) Should i be chasing NOX sensor issues? Def injector? bad SCR? Any input is appreciated.