Yes, I thought this would be obvious. More general, just take it as a proof of feasibility. 50 MHz is the transmitted fundamental frequency, the bit rate is 100 MBit/s. According to CAT 5 cable data, you can expect about 10 to 15 dB attenuation per 100 m at 50 MHz. In my opinion, the 100BASE-TX reference shows, what can be achieved with limited effort. Other standards are achieving higher data rates, e.g. 250 MBit/s per twisted pair with Gbit ethernet.
Without knowing the hardware details, it's impossible to determine the cause of the observed problems, I think.
Problem is hard to be scientist that must more investigate and alway improve opinions , Highly dope varium may make broken blood and using Toroid in circuit should beware cross magnetic couple leakage as balance current for long use Design.