Autofocus Backbutton focusing problems on 610

Set up the AE-L/AF-L button for back button autofocusing by selecting the menu for it and creating is as AF-On.
It worked seamlessly for about a week, and then suddenly it is working intermittently. i have tried it with three different
lenses and sometimes it works and sometimes it does not. I am at a loss, other than something is wrong here with the button
itself. Has anyone else tried this? I have found i often have to manually focus. Any ideas?
I might have to send my 610 back to Nikon.

I don't have a D610 but I have had difficulties with my D4's A/F 'freezing' and needing to be switched off and on to restore it.
The D4 has a dedicated AF-On button and it is currently back with Nikon who are trying to resolve it, (they've had it once for 6 weeks and failed to rectify the fault, now had it again for 3 weeks!).
Suggest you send it back to Nikon but as it's intermittent, like mine, be prepared to give the fullest details of settings/symptoms as you may well get a "we can't re-create the fault" response.

Hasn't happened with my D610. I do believe it's happened once or twice with a D600 or D7100, but I don't recall the conditions. I vaguely remember it may have had something to do with partially depressing the shutter as well, but I could be overthinking it for you. Intermittent, unreproducable issues are the worst. Hope it stops misbehaving, but it's better to get it checked rather than live with it forever.

I used it successfully on my D600, and now on my D610 with absolutely no problems at all. Sorry you're having problems because once you get used to it you'll never go back.

Both the back button and the shutter stopped activating autofocus. Brought it to Nikon and it is there for the repair.
They said it may take two weeks to diagnose and repair. The rep. asked me if i had dropped the camera, if it had been banged around. It is 5 months old and not a mark on it. It hadn't fallen, ever, or gotten banged up. He said he's never seen this issue before in a 610. I wonder if there is a more general problem or this is a problem for a small sample of cameras. Meanwhile, i will use my D7000, which i had packed away to sell. I can't stop thinking how nice the 810 felt in my hand, almost ergonomically perfect. Maybe they'll give me one by mistake!!!

Ha dreamer! I want a 810 too.