FCS Rx errors

[wwilts]

I have a 2530-24G connected to a 5406ZL over 1000SX fiber (OM1). The weirdest thing happens.

The 120 meter OM1 fiber is mounted on a ST breakbox. On the 5406ZL side it is connected with a ST-LC OM1 patch cable.

On the 2530 side:

If I use a ST-SC patch-cable connected to a SC-LC patch-cable using a SC-coupler, the link works fine.

If I use a ST-LC patch cable, as soon as I connect the outgoing connector to the 2530 all the leds light up steadily (with led-mode on Act).

I tried different SFP module, different patch cables. Auto mode and 1000-Full as duplex setting (on both ends). I cold booted the switch.

But everytime when I connect the rx connector, the link led lights up and the Act led start blinking (so it is receiving packets from the 5406ZL. But as soon as I plug in he tx connector, the leds freeze again.

In the port statistics I see a lot of FCS rx errors..