Summary of Translating Pages - section sequence
If any new section is added between existing sections, the system will allocate a section number. The number is used by the system to know where it came from and where the translated section must be placed, but to the translator it will appear out of sequence.
It is essential that during the markup phase care is taken to ensure sufficient context remains for the translators to make good judgements. Translators meeting bad examples should alert the admin group.