Assuming two things:
1.- That there is no defined order for the Update() function execution and that If a specific order is needed, you can define it yourself with the script execution order as specified here, and here.
2.- That the gameobjects are not updated according to their hierarchy as explained here
Something I could not clear out from the documentation is if you do not set any order for the script execution, once this is set 'randomly' by unity, if this order remains unaltered through the execution of the game or if the update execution order may change in time.
If you do not specify anything, the order won't be consistent. If you want a specific script to execute before others you HAVE to use the script execution order or use an array has suggested in you linked post.