check RJ45 mounting on board. if the solder pad is away from board, solder direct wires from rj45 to transformer

must connect to 10/100 base pulse transformer TS21AY Datasheet : http://www.bothhandusa.com/datasheets/filter-transformer/10-100-single-smd/TS21AY%20HF-RevA02-120531.pdf

Hardware design error. Problem is in the weak ETH socket mounting on the motherboard, the most common disconnects the first socket output.