[Observium] Ports switch are deleted after polling

I have more than 100 alcatel switches configured in my observium. All of these can be discoverd/polled properly.

However, I have 3 switches whose ports are deleted after the devices were added (I think after polling). When I run a discover again the ports show up in the GUI for a while, until the next polling. Other data such as vlans, temperature etc are always available. Other switches in the same environment does have normal behaviour. Of course the switch does operate normally all the time.

Any ideas or suggestions?

Thanks, Jan