This could be due to various factors, including:

• Hardware Issues: Faulty extension card, damaged cables, or incorrect connections.
• Software Problems: Incorrect configuration of the extension card, communication parameter mismatches, or software bugs.
• Network Interference: Noise or interference on the communication channel.
• Device Compatibility: Incompatibility between the extension card and the external device.

Troubleshooting Steps:

1. Check Hardware:

   • Inspect the extension card for any physical damage or loose connections.
   • Verify that the cables connecting the extension card to the drive and the external device are securely plugged in.
   • Use a cable tester to check the integrity of the cables.
   • If possible, try using a different extension card or cable to isolate the problem.

2. Verify Software Configuration:

   • Ensure that the extension card is correctly configured in the drive's software. Refer to the drive's user manual for specific instructions.
   • Check that the communication parameters (baud rate, parity, stop bits, etc.) match between the drive and the external device.
   • If the extension card uses a specific protocol (e.g., Modbus, CANopen), verify that the protocol settings are correct on both devices.

3. Check for Network Interference:

   • If the extension card is connected to a network, try moving it away from other electronic devices that might be causing interference.
   • Use a shielded cable to reduce the susceptibility to electromagnetic interference.

4. Test Device Compatibility:

   • If possible, try connecting a different external device to the extension card to see if the frame loss persists.
   • If the problem is specific to a particular device, it may be incompatible with the extension card or the drive.