Sorry to bother you but how did you end up fixing this?
This thread is the first result when trying to search this problem, it might be useful if there was something here for those of us still struggling.
If your utility classes (containing only static functions) access autoloads (global singletons) or global functions—or conversely, if autoloads call these static classes during initialization—then everything might work fine in the editor (or when running from the editor) but break in the exported build.