PAC Server issues in China - error 504 Gateway timeout

Hi,
we have some issues at one of our locations in mainland China.
Locations has two IPSec tunnels opened and the PAC file is fetched via IPSec / via the Public Services Edges.

Customer now often gets http 504 as return code, almost 50% depending on the used PAC Server.
For Germany, we have the same setup (PAC files fetched via IPSec) and we see 100% success rate.

Obviously “something” blocks the traffic between the PSE and the PAC server.

pac

Related case number: 02602820
Best regards
Andreas