That's very weird, the only think I can suggest you is to forget the device, upgrade in standalone mode, adopt.. there must be something wrong with the connection between your client and the...

@TReimann Did you reboot the router ? what's the current memory consumption ?

@trigg3r both ends need - in general - to link at the same speed. while sfp+ devices usually work fine in sfp slots at 1gig.. I suggest you ask the vendor if they do gigabit just to be absolutely...

@trigg3r yes, you need to buy a gigabit ethernet SFP transceiver. Now, should you ? No, you shouldn't. if the device you want to connect on the other side is less than 7 meters away. use a passive...

@jra11500 Yes, the cheapest way is to replace all cables and jacks.

@jra11500 this usually means there is indeed some trouble in the cabling..I suggest you, since they are extremely expensive, to RENT a cable certifier (rather than a tester) Fluke CableIQ or LinkIQ...