Solving the random issues that result from going beyond the specs of the cabling is the worst. It works for months and then suddenly fails for no reason.
This hasn't been my experience with copper. It tends to work until someone breaks it. Optical SFP's OTOH, were my bane for many years as they do frequently degrade leaving a once perfectly functional link dropping some huge number of packets before anyone notices that the link has degraded to some 1980's level of speed. Port monitoring when your not a network provider, or big data center seems to be a "hard" problem.