Your fill words are different... One switch is set to 0 and the other is set to 1.
I'd set them both to 0.
Not a switch setting (to be clear). Fill Word is a port setting.
Richkell is right, fillword in both ends should be the same. But in this case, if working at 2G, the fillword settings configured at port level will not be taken into account.
Many times, the restrictions are stablished by 4he dwdm array. In order to see what config is best for the isl stability try to lock the ports as E-port, disable vc link init and/or enable r_rdy mode.