Network topology
Fritz!Box 7590
Port 1 → TP‑Link TL‑SG105PE (connected to Deco X50, the mesh master)
Port 2 → TP‑Link TL‑SG1016DE (connected to Deco M4 node)

Symptom on TL‑SG1016DE

• At random intervals (days or weeks), the Power LED, the Uplink Link/Act LED (port status), and the port LED for the Deco M4 all start blinking in sync.
• Loop Prevention enabled → blink happens.
• Loop Prevention disabled → blinking stops immediately.
• Re‑enabling Loop Prevention after the event does not reproduce the blink until some later, unpredictable time.
• Storm Control is off—it’s not rate‑limiting broadcasts.
• Traffic continues to pass normally throughout; no outages.

Possible trigger
Often correlates with a prolonged Internet outage on the Fritz!Box (but the Deco’s Intelligent DHCP fallback is disabled, so they shouldn’t be renegotiating addresses).

Similar behavior in office
On Omada switches with Datto (Kaseya) APs, you sometimes see the same “link + AP” blink pattern, suggesting a Layer 2 loop detection kicking in.

Is this a known issue? Fix? Any other ideas?
Mine are hypotheses based on what I’ve observed.