Wireguard's official Android app (Go implementation). But the behavior persists over other implementation as well, like Cloudflare 1.1.1.1 app (for its Warp service) and Proton VPN.
Funny thing is, when I get back home and it connects to WiFi, WireGuard just works, no need to disconnect, reconnect, anything. But just as I roam AP, this thing happens. I go into more detail and circumstance of this behavior in this thread—that I couldn't figure out what's going on and couldn't find documentation is why this thread came to be.