Support Drakensang map loading extremely slow on Vodafone FTTH, but works normally via mobile data

Hi everyone,
I'm experiencing a strange connection/loading issue with Drakensang.
When I play using my home Internet connection (Vodafone FTTH), the game takes a very long time to load certain areas/maps. Sometimes it appears to be stuck for quite a while during the loading process.
However, if I connect the exact same PC to the Internet through my mobile phone's hotspot/mobile data, the same area loads almost immediately.
I recently upgraded the home connection from Vodafone copper/DSL to Vodafone FTTH, and the issue is still present with the new fiber connection.
So far, this is what I have observed:

• Vodafone FTTH → very slow loading of the affected area
• Mobile data/hotspot → loads almost immediately
• Same PC and same game installation
• No other noticeable Internet problems
• The connection speed itself appears to be normal

I am currently testing different network settings, including IPv6 and DNS, to see whether the problem is related to routing between Vodafone and the Drakensang servers.
Could this be related to the server connection, routing/peering, IPv4/IPv6, or a specific network path used by Vodafone?
If you need any additional information (traceroute, ping, IP information, logs, etc.), I can provide it.