Have the same router (Flint 2), and had a similar issue in the past. After I configured SSIDs with different names on the radios (i.e. the SSID is either configured on radio0 or radio1, not both), I didn't encounter this anymore. YMMV, but this helped me - perhaps it'll prove useful to you as well.

And besides this issue, overall it works great. I recommend this to anyone who asks me about it.