Ac losing refrigrant over a period of four days

[soon@vancom.co.za]

I am experiencing ongoing issues with the ac system in my MK5 GTI. The system was regassed once, but the refrigerant lasted only four days. A second regas was performed, this time with the inclusion of dye to detect potential leaks, yet the refrigerant again lasted only four days. Despite these attempts, the technicians have been unable to locate any leaks. Could you please advise on potential causes or next steps to resolve this issue?

[Flyingscotsman]

Could be multiple points of leak, but the pressure sensor failing is common.  Number 18 on diagram below. Its usually the o-ring (number 47) that perishes. Easy replacement but tricky to access with a spanner.

https://volkswagen.7zap.com/en/rdw/golf+variant+4motion/golf/2008-625/2/260-260041/#18