I'm experiencing a critical issue with VLAN isolation on my TL-SG1024DE.

Problematic Setup:

• TL-SG1024DE: Configured with Port-Based VLAN 10 (Ports 1-18, untagged) and VLAN 20 (Ports 19-24, untagged)

• MikroTik hEX S: Functions as a transparent Layer 2 bridge (hw=off on all ports). ether1 connects to a VLAN 10 port (e.g., Port 18) on the TL-SG1024DE, and ether2 connects to a VLAN 20 port (e.g., Port 24) on the TL-SG1024DE

• Symptom: My network experiences extreme lag, packet loss, and timeouts, becoming almost unusable

Key Evidence (MAC Flapping): MikroTik sees "MAC Flapping" for devices residing solely in VLAN 10 (e.g., FritzBox MAC 3C:A6:2F:03:E9:0A). This MAC repeatedly appears on both ether1 (VLAN 10 uplink) and ether2 (VLAN 20 uplink) within the MikroTik bridge.

Crucial Observation: This problem occurs immediately when ether2 (VLAN 20 uplink) is connected to the TL-SG1024DE, even with no other devices attached to VLAN 20. Disconnecting ether2 instantly stabilizes the network.

Working Setup (Comparison): When I replace the TL-SG1024DE's VLAN function by using two separate physical switches (one for the VLAN 10 segment, one for VLAN 20 segment), the network is 100% stable with no issues or MAC flapping, using the identical MikroTik configuration.

Conclusion: This indicates that the TL-SG1024DE fails to properly isolate Layer 2 traffic between its configured Port-Based VLANs (VLAN 10 and VLAN 20). Traffic leaks between them, creating an uncontrolled loop via the MikroTik bridge.

Has anyone else experienced this, or are there known firmware fixes for this VLAN isolation defect?