iOS app remote access via nginx proxy -> no sitemaps

Im using a nginx proxy for remote access. Since OH5 (or since an app update?), the iOS app does not retrieve a sitemap list, or does not request it. What I see in the nginx log:

194.230.161.186 - master [07/Oct/2025:19:51:23 +0200] "GET /rest/ HTTP/1.1" 200 504 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"
194.230.161.186 - master [07/Oct/2025:19:51:23 +0200] "GET /rest/ui/tiles? HTTP/1.1" 200 133 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"
194.230.161.186 - master [07/Oct/2025:19:51:23 +0200] "GET /rest/ HTTP/1.1" 200 504 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"
194.230.161.186 - master [07/Oct/2025:19:51:23 +0200] "GET /habpanel/tile.png? HTTP/1.1" 403 169 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"
194.230.161.186 - master [07/Oct/2025:19:51:23 +0200] "GET /habpanel/tile.png? HTTP/1.1" 403 169 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"
194.230.161.186 - master [07/Oct/2025:19:51:23 +0200] "GET /rest/ui/tiles? HTTP/1.1" 200 133 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"
194.230.161.186 - master [07/Oct/2025:19:51:23 +0200] "GET /habpanel/tile.png? HTTP/1.1" 403 169 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"
194.230.161.186 - master [07/Oct/2025:19:51:23 +0200] "GET /habpanel/tile.png? HTTP/1.1" 403 169 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"
194.230.161.186 - master [07/Oct/2025:19:51:24 +0200] "GET /habpanel/tile.png? HTTP/1.1" 403 169 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"

Before, the log looked like that:

45.131.77.218 - master [27/Sep/2025:16:44:03 +0200] "GET /rest/ HTTP/1.1" 200 504 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"
45.131.77.218 - master [27/Sep/2025:16:44:03 +0200] "GET /rest/sitemaps?limit=20 HTTP/1.1" 200 484 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"
45.131.77.218 - master [27/Sep/2025:16:44:03 +0200] "GET /rest/ HTTP/1.1" 200 504 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"
45.131.77.218 - master [27/Sep/2025:16:44:03 +0200] "GET /rest/ui/tiles? HTTP/1.1" 200 133 "-" "openHAB/11 CFNetwork/3860.100.1 Darwin/25.0.0"

In the old log, I can see sitemap GET requests.
I also tried the testflight app, but there I have the same problem.
Anybody else having trouble with the remote access ?

Btw, i can still access the iOS sitemap via VPN, but this solution is not preferable for my family members.