FWIW, I’ve been experiencing the bogus IP addresses in Roon since at least 2019, when I was using these AEs with a different router - Apple Time Capsule.
Here’s a link to that old thread if anyone is interested. Post # 9 and 15 are relevant.
Apologies to @Reamonn_Lenkas for hijacking your thread, but I thought you might be intereested.