Also learned this the hard way, when i was starting my “homelab” , I bought a box of (not knowingly that its bad) cheap CCA(copper clad alum) cat6 cables and im wondering why are my access points not negotiating to gigabit, turns out cca are trash and shouldn’t be used on POE or even on high speed trunks, learned my lesson now and swapped my cables to pure copper, they are more expensive like 100$ more expensive but at least they do the job.