I didn't have problems with the DIR-890L I had...but my ASUS was giving me issues.
Smart Connect off - and all 3 bands had the same SSID.
The camera would connect and get dropped repeatedly on 2.4Ghz.
11. 2016-10-07 07:25:39 NETWORK INTERFACE CHANGE TO ETHERNET
12. 2016-10-07 07:25:11 NETWORK LOSS
13. 2016-10-07 07:25:03 NETWORK RECONNECT
14. 2016-10-07 07:25:00 NETWORK LOSS
15. 2016-10-07 07:24:52 NETWORK RECONNECT
16. 2016-10-07 07:24:38 NETWORK LOSS
I renamed the routers 2.4Ghz connection to "router-2.4G"...and connected the camera to that, and it is no longer a problem.
Well - I post this in case anyone else runs into this issue (Asus RT-AC3200 f/w 3.0.0.4.380_3479 (latest as of this today))