Slow file transfer to Synology Nas since router reset

I was getting good transfer speeds between my Windows 8.1 laptop and the mapped network drive 'music folder' I created when I first connected the Synology DS215j .
I had a problem with my router so had to do a default reset.
I am now getting extremely slow transfer speeds over the ethernet connection.

Any idea what setting on the router I need looking at or if it could be something else?

Could it have something to do with port forwarding?

Thanks

Anyone?

Reset. To default settings we've had switches and routers at work suddenly decide they you g to run at 10MB haven't added any new hardware?

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