If you have distributed the links via email, then you can download the distribution report to track what the status is and how many people have completed the survey. This will give you a fair bit of idea as to why there is a discrepancy between the responses that you are viewing vs what the company claims the response rate should be

https://community.qualtrics.com/XMcommunity/discussion/comment/44862#Comment_44862Many thanks! We are not using email distribution. Just anonymous link and QR code...

Unfortunately for anonymous links, its hard to track users whether they have completed the survey or not

https://community.qualtrics.com/XMcommunity/discussion/comment/44879#Comment_44879thanks for the clarification!

UPDATE:
The company contact point tested the survey himself just now, submitting two test responses using the two low-participation functions respectively. I only received one of them (have looked into both recorded and in-progress entries). He confirmed that he had gone through exactly the same process.
He observed that there's a difference between what people chose and what Qualtrics recorded (e.g., people chose QA as their function, but Qualtrics reports said Internal Audits). These issues are prevailing only when our French translation is used.
We are using anonymous link so I'm aware that it is difficult to trace, but what may be the issue here?
Thanks in advance!