I found another article that may be of interest. Its highly detailed about surge damages to ethernet ports.
Designing Ethernet Cable Ports to Withstand Lightning Surges
a clip from the section on gpr
"
Ground Potential Rise
When lightning strikes the ground, currents up to 100 kA flow through the soil toward the center of the earth. However, since the soil has a finite resistance, the lightning current IL spreads out in many directions, represented by IL1, IL2, and IL3 in Figure 4. This creates a voltage gradient that can be represented as a set of equipotential half-spheres, indicated by the blue lines in Figure 4.
If there are two devices nearby that each have a separate reference to ground, the surge current IL1 flowing through the soil creates a momentary difference VDIFF in the potential at the two separate ground points GND1 and GND2. This voltage difference can be several thousand volts if the lightning strike is nearby. Reference [1] contains a more detailed description of the mechanisms that lead to GPR.
Figure 4 shows a mechanism called ground potential rise (GPR). GPR is perhaps the most complicated mechanism to explain, but it is often the root cause of surge failures on communication cables."
Also if you read further in the comments there are others that suspect issues from having different ground references.