I encountered this issue this morning, which took my 5Ghz network offline:
2018-10-11 05:26:56 warning kernel[]: [ 258.911673] WARNING: CPU: 0 PID: 2942 at /home/beast/beast/workspace/omnia-stable/build_dir/target-arm_cortex-a9+vfpv3_musl-1.1.15_eabi/linux-mvebu/compat-wireless-2017-01-31/net/mac80211/driver-ops.h:17 ieee80211_iter_keys_rcu+0x5b4/0x86c [mac80211]()
2018-10-11 05:26:56 warning kernel[]: [ 258.911682] wlan0: Failed check-sdata-in-driver check, flags: 0x9
2018-10-11 05:26:56 warning kernel[]: [ 258.911689] Modules linked in: qcserial option iptable_nat ath9k usb_wwan snd_usb_audio rndis_host qmi_wwan pppoe nf_nat_pptp nf_nat_ipv4 nf_nat_amanda nf_conntrack_pptp nf_conntrack_netlink nf_conntrack_ipv6 nf_conntrack_ipv4 nf_conntrack_amanda ipt_REJECT ipt_MASQUERADE ebtable_nat ebtable_filter ebtable_broute cdc_ether ath9k_common armada_thermal xt_time xt_tcpudp xt_tcpmss xt_statistic xt_state xt_recent xt_nat xt_multiport xt_mark xt_mac xt_limit xt_length xt_id xt_hl xt_helper xt_ecn xt_dscp xt_conntrack xt_connmark xt_connlimit xt_connbytes xt_comment xt_TCPMSS xt_REDIRECT xt_LOG xt_HL xt_DSCP xt_CT xt_CLASSIFY usbserial usbnet ums_usbat ums_sddr55 ums_sddr09 ums_karma ums_jumpshot ums_isd200 ums_freecom ums_datafab ums_cypress ums_alauda ts_kmp ts_fsm ts_bm thermal_sys snd_usbmidi_lib pppox ppp_mppe ppp_async nfnetlink nf_reject_ipv4 nf_nat_tftp nf_nat_snmp_basic nf_nat_sip nf_nat_redirect nf_nat_proto_gre nf_nat_masquerade_ipv4 nf_nat_irc nf_nat_h323 nf_nat_ftp nf_nat nf_log_ipv4 nf_defrag_ipv6 nf_defrag_ipv4 nf_conntrack_tftp nf_conntrack_snmp nf_conntrack_sip nf_conntrack_rtcache nf_conntrack_proto_gre nf_conntrack_irc nf_conntrack_h323 nf_conntrack_ftp nf_conntrack_broadcast mvsdio iptable_raw iptable_mangle iptable_filter ipt_ECN ip_tables hwmon ebtables ebt_vlan ebt_stp ebt_redirect ebt_pkttype ebt_mark_m ebt_mark ebt_limit ebt_among ebt_802_3 crc_ccitt cdc_wdm ath9k_hw fuse sch_cake sch_teql sch_tbf sch_sfq sch_red sch_prio sch_pie sch_netem sch_htb sch_gred sch_fq sch_dsmark sch_codel em_text em_nbyte em_meta em_cmp cls_basic act_vlan act_police act_pedit act_nat act_ipt act_gact act_csum act_bpf act_connmark nf_conntrack act_skbedit act_mirred em_u32 cls_u32 cls_tcindex cls_flow cls_route cls_fw sch_hfsc sch_ingress ath10k_pci ath10k_core ath mac80211 cfg80211 compat ledtrig_usbdev ledtrig_oneshot xt_LED ledtrig_morse ledtrig_heartbeat ledtrig_gpio cryptodev ip6t_REJECT nf_reject_ipv6 nf_log_ipv6 nf_log_common ip6table_raw ip6table_mangle ip6table_filter ip6_tables x_tables pppoatm ppp_generic slhc nfsd nfsv3 msdos ip_gre gre ifb sit ip6_tunnel tunnel6 tunnel4 ip_tunnel veth tun snd_compress snd_pcm_oss snd_mixer_oss snd_pcm snd_timer snd_rawmidi snd_seq_device snd_hwdep snd input_core soundcore rxkad vfat fat udf crc_itu_t ntfs nfs_layout_nfsv41_files nfsv4 nfs auth_rpcgss oid_registry lockd sunrpc grace minix isofs hfsplus hfs cramfs configfs cifs autofs4 kafs af_rxrpc dns_resolver dm_crypt dm_mirror dm_region_hash dm_log dm_mod br2684 atm multipath fscache raid456 async_raid6_recov async_pq async_xor async_memcpy async_tx raid10 raid1 raid0 linear md_mod nls_utf8 nls_koi8_r nls_cp1255 nls_iso8859_6 nls_iso8859_2 nls_iso8859_15 nls_iso8859_13 nls_iso8859_1 nls_cp932 nls_cp866 nls_cp864 nls_cp862 nls_cp852 nls_cp850 nls_cp775 nls_cp437 nls_cp1251 nls_cp1250 xts algif_skcipher algif_hash af_alg sha512_generic sha256_generic sha1_generic seqiv jitterentropy_rng drbg pcbc md5 md4 marvell_cesa hmac gf128mul fcrypt ecb des_generic ctr cmac ccm cbc authenc xhci_plat_hcd xhci_pci xhci_hcd uhci_hcd ledtrig_transient ehci_orion ehci_platform ehci_hcd ahci_platform uas usb_storage xfs libcrc32c jfs f2fs exfat usbcore nls_base usb_common mii aead crypto_null
2018-10-11 05:26:56 warning kernel[]: [ 258.912192] CPU: 0 PID: 2942 Comm: kworker/0:2 Tainted: G W 4.4.157-0a333a8e606ab056173befac424900d2-1 #1
2018-10-11 05:26:56 warning kernel[]: [ 258.912196] Hardware name: Marvell Armada 380/385 (Device Tree)
Link to whole stacktrace on pastebin. The uptime was at about 1h30m and I made a copy of /var/log/messages before rebooting. Will update this thread if I encounter it again. 