[Q] Wired connection slower than WiFi? topic

My fire tv running Kodi or SPMC has the strange behavior that playing movies from a SMB share (Apple time capsule) with wired connection is buffering, but not on WiFi.

I've already replaced the ethernet cable and used another port an the time capsule, but the problem is still the same.
Is it possible that the network stack on fire tv is bad on wired connections only?

Thanks!