Fixing campus network... Found this gem...
I was helping a church & school this past week resolve a bunch of UniFi related issues. Old guy from out of state had installed a UDM Pro, various Pro switches... and AC-Pro's... In my diagnosing I found that 1 of the AC-Pro's (One that was actually... plugged in...) was negotiating at 100mb/s, I looked at the programming as with the other issues I was finding it wouldn't have surprised me if it was manually set, but no it was correct. I put my Fluke meter on the uplink from the AP and saw that I had 1&2 and 3&6 only connected to the switch... "Weird"... I thought making my way to the IDF to see what they'd messed up... and I pulled this patch cable out of the switch.
Edit 2: Added clarification, Yes, I'm fully aware this these exist and what it is, there is some satire as a part of this post, what I don't know is what would make someone think it was OK to install (patch cable at rack) in 2021, when this was done. The installer was paid... Handsomely... For shotty work.
Why... Did this ever exist...?... (Edit: Sarcasam... I know technically why it exists, been doing this a long time)
(So many other problems from the previous deployment... (unplugged AP's, Injectors connected when a POE switch was 6" away... etc... etc... etc...) this is just the most notable problem.