The best overloaded method match for 'System.Collections.Generic.List<RM2ExCoop.RM2C.F3DCommand>.this[int]' has some invalid arguments

[boilus-platform]

[INFO] Starting Text
[INFO] Text done
[INFO] Starting Misc
[INFO] Misc done
[INFO] Starting Levels
[INFO] Exporting Level 6
RuntimeBinderException:
The best overloaded method match for 'System.Collections.Generic.List<RM2ExCoop.RM2C.F3DCommand>.this[int]' has some invalid arguments

at CallSite.Target(Closure , CallSite , List1 , Object ) at RM2ExCoop.RM2C.F3D.OptimizeModelData(List1 modelData)
at RM2ExCoop.RM2C.F3D.ModelWrite(Rom rom, List1 modelData, String dir, String idPrefix, String levelDir, Boolean optimize) at RM2ExCoop.RM2C.Rom.WriteLevel(String levelDir, Script script, Options options, List1 allWaterBoxes, List1 m64Files, List1 seqNums)
at RM2ExCoop.RM2C.Rom.ExportLevel(Int32 levelId, StreamWriter lvldefs, Options options, List1 allWaterBoxes, List1 m64Files, List`1 seqNums)
at RM2ExCoop.RM2C.Main.Run(String romPath, Options options)
at RM2ExCoop.MainWindow.<>c__DisplayClass2_0.<RM2CBtn_Click>b__0()