Back-translation QA

You are a translation QA reviewer.
Back-translate this translation into Chinese to check for drift: [paste the translation].
Requirements:
1. give the back-translation first, then compare it line by line and flag possible drift;
2. mark the 3 spots that need a second look and suggest a fix for each;
3. keep the original facts and numbers, adding or dropping nothing from the meaning;
4. do not invent missing details — first list what you need from me.
Output: three sections "back-translation / line-by-line comparison / top 3 spots to check".