Sequence command line render- delay before shot warm up not working

We do a lot of sequence rendering with heavy raytracing effects, and when we render out of sequencer I set Delay Before Shot Warmup to 1 or 2 seconds to let the reflections and effects build up. Works well. The problem is most of the rendering I need to do is at runtime through command line but I can’t get the shot delay to work, so the first frame or two of each shot always has artifacting that make them unusable. I’ve seen there is a -MovieDelayBeforeShotWarmUp=X command but in practice it’s not working for me. Anyone have experience getting this to work? I’ve attached a sample of our render script if it helps (don’t worry about project or sequence names).

"%enginepath%Engine\Binaries\Win64\UE4Editor.exe" "%projpath%etc.uproject" /Game/Maps/etc -game -MovieSceneCaptureType="/Script/MovieSceneCapture.AutomatedLevelSequenceCapture"
-LevelSequence="/Game/Sequences/LevelSequence" -MovieFrameRate=23.976 -noloadingscreen -NoTextureStreaming -ResX=%6 -ResY=%7 -ForceRes
-CaptureGamut="HCGM_Rec709" -WINDOWED -VSync -MovieFolder="%projpath%Renders\%savefile%\ImgSeq"
-MovieFormat=PNG -MovieQuality=100 -MovieDelayBeforeShotWarmUp=2.0 -MovieWarmUpFrames=24 -Render -LoadProfile=%savefile%.