Yes, switches definitely fail. While they're generally reliable, they are electronic devices, and like any such device, they can be subject to failure. Here's a breakdown of why switches fail and what might be happening in your situation

Why Switches Fail:
Age

Electronics degrade over time. Components like capacitors can dry out or become less efficient, affecting performance.

Heat

Switches, especially those passively cooled (no fan), can overheat, especially if located in a confined space with poor ventilation. Overheating accelerates component degradation.

Power Surges/Fluctuations

Even if you have surge protection, minor fluctuations or infrequent surges can still stress the components over time. A power outage, even a brief one, can sometimes be enough to push a weakened component over the edge.

Physical Damage

While less common, accidental bumps, drops, or even static electricity discharge can damage a switch.

Software/Firmware Issues

While less common on basic unmanaged switches like the GS108, corrupted firmware can cause erratic behavior. (Managed switches with complex features are more prone to this.)

Overloading

Unlikely with a simple home setup, but theoretically, extremely high network traffic could theoretically stress the switch, although the GS108 is designed to handle its rated throughput.

Marginal Cable Connections

It's not always the switch, but the connection to the switch. A slightly loose or corroded RJ45 connector can cause intermittent issues.

Possible Causes in Your Specific Scenario

Your "check cable" message strongly points to a connectivity issue. Here's how the sprinkler system, VFD, PLC, and HMI could be involved:1.

Electrical Interference (EMI)

This is the MOST likely culprit, given the timing with your sprinkler system/VFD.

VFD (Variable Frequency Drive)

VFDs are notorious for generating significant electrical noise (EMI). They rapidly switch high voltages to control motor speed, which creates radio frequency interference that can disrupt Ethernet signals.

Sprinkler Wiring

Even if the sprinkler wiring itself isn't directly interfering, the motor starting and stopping can cause voltage fluctuations or ground loops.

Grounding

Improper grounding of your VFD, PLC, HMI, or even the sprinkler system can create ground loops. These ground loops act as antennas, picking up and radiating EMI that can interfere with network communication.2.

Power Supply Issues (Related to EMI)

The VFD's operation might be putting a strain on your electrical circuit, causing voltage dips. These dips, while probably not drastic enough to be noticeable with lights, could affect the sensitive electronics in your switch, PLC, or HMI. A failing power supply in any of your devices (including the switch itself) can cause unpredictable behavior.3.

IP Address Conflicts

Very unlikely, but worth a quick check. If you're using static IP addresses, make sure there are no duplicates. DHCP is less prone to this but still check.4.

Cable Issues (More likely now)

While your wiring might be Cat5, a compromised cable close to the switch or a device could be more susceptible to EMI when the VFD is running. A nick in the cable, a poorly crimped connector, or even excessive bending can make the cable act as an antenna for EMI. The vibration from the sprinkler system's pump could be subtly loosening a cable connection somewhere.5.

Switch Degradation (Less likely, but still possible)

The switch could be failing, and the EMI is simply exacerbating the existing problem. A weak port might be more sensitive to interference.

Troubleshooting Steps (Prioritized by Likelihood)


Isolate the EMI Source (Most Important)



Simplest Test

Can you reliably reproduce the "check cable" error only when the sprinklers/VFD are running? If so, that strongly implicates EMI.

Turn off the Sprinklers/VFD

Does the problem disappear immediately when the sprinkler system is turned off? If so, you've confirmed that it's the source of the interference.2.

Address EMI Mitigation (If EMI is the problem)

This is the trickiest part.

Grounding



First, and most important

Ensure everything is properly grounded. This includes the VFD, PLC, HMI, and any metal enclosures. Consult the VFD's manual for specific grounding instructions. A proper earth ground is essential.

Shielded Ethernet Cables

Replace your existing Cat5 cables (especially the ones near the VFD, PLC, and HMI) with

Cat5e or Cat6 shielded Ethernet cables (STP). Make sure the shield is properly grounded at both ends (this is critical). Ferrite Beads

Clamp ferrite beads around the Ethernet cables near the VFD, PLC, and HMI. These beads help filter out high-frequency noise.

Distance

Increase the physical distance between the VFD/PLC/HMI and the network switch/Ethernet cables if possible. The further away, the less interference.

VFD Filters

Some VFDs have built-in filters or allow for the addition of external filters to reduce EMI. Check the VFD's manual.

Dedicated Circuit

Ensure the VFD is on a dedicated electrical circuit, separate from the circuit powering the switch, PLC, and HMI. This can help isolate voltage fluctuations.

Quality Power Supply

Use a high-quality, surge-protected power strip or UPS for the switch, PLC, and HMI.3.

Check Cables and Connections

Carefully inspect all Ethernet cables for damage, especially near connectors. Reseat all Ethernet cables in the switch, PLC, HMI, and any other devices. Make sure they click into place firmly. If possible, test with known good Ethernet cables. Use a cable tester to verify the integrity of each cable run (continuity and proper wiring).4.

Test the Switch

If you have a spare switch, swap it in to see if the problem disappears. This is the most direct way to determine if the switch itself is failing. Try different ports on the switch.5.

Power Cycle Everything

Completely power down the switch, PLC, HMI, VFD, and sprinkler system. Wait a few minutes, then power them back up in a controlled sequence (e.g., switch first, then PLC, then HMI, then VFD/sprinklers).6.

Firmware (Less likely on a GS108, but check)

Check the Netgear website for the latest firmware for your GS108 switch. Although unlikely for a basic unmanaged switch, it's worth checking if a firmware update is available.7.

IP Address Check (Least Likely)

* Double-check that no devices have the same IP address.

In Summary:

The most likely cause is EMI from the VFD/sprinkler system affecting your Ethernet network. Focus on proper grounding, shielded cables, ferrite beads, and physical separation to mitigate the interference. If the problem persists after addressing EMI, then consider the switch itself might be failing or there is a cable issue. Good luck! Flag for review