There are also distance limits based on the type of cable used and the power drawn by the end device. The more you push that, the more heat you build. Shielding reduces that heat factor.

https://en.wikipedia.org/wiki/Power_over_Ethernet#Power_capa...

For Dayjob I power a lot of very expensive not-even-on-the-market-yet radios and other equipment via multiple PoE standards, mixed vendors, 2 pair, 4 pair, etc via POE and we have ran into all kinds of POE problems over the years.

POE fires do happen. Sometimes it's the cable, the connector, sometimes something happened to the cable run. Sometimes the gear melts.

https://www.powerelectronictips.com/halt-and-catch-fire-the-...