I had troubles connecting my t95max with 1 Gbit, too. As soon as i told the router to switch to 100Mbit for that particular port, it worked. My guess was the port on that box is broken or doesn't have all neccessary wires connected for stable Gbit. Might be the same for you.
Solution: get a cheap USB-Ethernet/Gbit adapter. Libreelec will detect it as ETH1 and you can use it with full speed then. Be warned that android itself does not detect it, so this will only help you in LE.
oh crazy t95max thx for your answer will order 1 from ebay right now