Unknown black component on PCB
simulate this circuit &ndash; Schematic created using CircuitLab

The patent

The purpose of this ferrite Balun here is to attenuate unwanted noise in RF band on the DC line used by RF amplifiers.

Heat is an indication of high RF CM noise either radiated or conduction on DC power line from card edge due to unbalanced , unshielded DC external wires acting as antenna.

There may be a fault in the load causing this to heat up.