urtwn0: ieee80211_crypto_encap returns NULL

[Otacílio]

I'm get instability when using my beaglebone black to transmit video by 
wifi. The urtwn randomly disconnects and this time I got this error:

Network is down
urtwn0: ieee80211_crypto_encap returns NULL.
urtwn0: ieee80211_crypto_encap returns NULL.
urtwn0: ieee80211_crypto_encap returns NULL.
urtwn0: ieee80211_crypto_encap returns NULL.
urtwn0: ieee80211_crypto_encap returns NULL.

I'm using  FreeBSD 11.0-BETA4 #0 r303242M


[]'s

-Otacilio