Dual PS5 on Same Network – PSN Party Delay & Hit Registration Issues

[Sarin]

Hello everyone,
I’m experiencing an issue and wanted to ask if anyone here might have a solution.
In my household, I have two PlayStation 5 consoles that are used at the same time to play the same games and communicate via PSN Party. When joining a PSN Party, it takes about 30 seconds before we can actually talk to each other.
Additionally, in games like Battlefield 6 and Call of Duty, we often encounter hit registration issues — we shoot at enemies, but the bullets don’t seem to register properly.
Interestingly, when the two PS5 consoles are not on the same network, everything works perfectly:

• Voice chat in PSN Party works instantly
• Hit registration is normal

My network setup:

• Vodafone Cable 1 Gbps
• FRITZ!Box 6660 (bridge mode)
• ASUS GT-BE98 router (firmware: 3.0.0.6.102_39244)
• ASUS RT-AX88U mesh node (firmware: 3.0.0.4.388_24346)
• Both PS5 consoles are connected via LAN to the GT-BE98
• UPnP is enabled

If this issue cannot be solved with my current hardware, are there alternative setups or hardware recommendations that could fix this?
Also, I originally wrote this post myself and used ChatGPT to translate it into English, as my English is not very strong.

Thank you in advance!