vbp 5.7 : visual build pro action spawns child with missing system macros?

[epu]

still looping through the continual build script. saving the macro values out on every step seems to be preventing the original issue (hasn't shown up yet). is there some kind of flush done on macros when you save them out that isn't done normally during a build, or a timing problem that the build script functionality is now masking out?