Any chance you could update the CMasking_Mask render element to either use iterative letters or even add an underscore after the number?
If kept at default it doesn't work for animation and needs to be renamed. For example, CMasking_Mask001 frame 01 becomes CMasking_Mask0010001 so AE/Fusion thinks it is frame 10,001
not a big request, but would speed my day up by a few seconds