[ubuntu] Wifi coect on dual-boot laptop fails in Ubuntu, but not Mac OS X

I'm ruing Ubuntu Desktop 16.04 on a MacBook 13" (on which I also dual-boot Mac OS X 10.7.5). This laptop has a Broadcom wireless card: "Broadcom BCM4328 802.11 Wireless Controller" according to Mac OS X. In Ubuntu, I'm using the proprietary Broadcom STA Wireless Driver. I coect the laptop wirelessly to a TP-Link WDR-3600 wifi router, which is ruing OpenWRT 15.05.1. It has two Atheros wifi chips built in, one for the 2.4GHz band and one for the 5GHz band. I have a separate SSID for each band, but both are set up with the same authentication credentials. In OpenWRT, the hardware for the 2.4GHz band is listed as "Generic MAC80211 802.11bgn" and the 5GHz band is listed as "Atheros AR9580 802.11an".

The problem I'm experiencing right now is that, when I choose to coect to the 2.4GHz band SSID using Ubuntu, my passphrase is accepted, and the coection seems to negotiate for a minute or so, and then either shows as discoected, or shows as coected but has no IP coectivity. Either way, there is no actual IP coectivity when I try to ping other hosts or browse the web. If I then attempt to coect to the 5GHz band SSID, the coection is successful almost immediately, and ping/web browsing/etc works normally. The problem with coecting to the 2.4GHz band persists across deleting/recreating the wireless coections in the network manager, as well as across reboots.

When I reboot the computer into Mac OS X and try to coect to the 2.4GHz network, it works immediately, as does the 5GHz network.

No other Mac or Linux computers, or iDevices, in the household are having this same issue.

I'm trying to determine whether the problem lies in the computer hardware, operating system, router hardware, or router operating system, or if it's some unique combination of all four factors that causes the issue. Right now, my best guess is that Ubuntu's DHCP client isn't getting along well with OpenWRT's DHCP server, but I'm not sure why or who's to blame, or what to do further to diagnose the issue.

If anyone has suggestions on how to proceed, please let me know. I've included relevant log file data as Gists on Github. I plan to cross-post this in the OpenWRT forums.

Coecting from Ubuntu:
Syslog from Ubuntu when trying+failing to coect to the 2.4GHz band: ubuntu_syslog_2.4GHz.txt
Syslog from Ubuntu when coecting to the 5GHz band: ubuntu_syslog_5GHz.txt
Syslog from OpenWRT when trying+failing to coect to the 2.4GHz band: openwrt_syslog_2.4GHz.txt
Syslog from OpenWRT when coecting to the 5GHz band: openwrt_syslog_5GHz.txt

Coecting from Mac OS X:
Syslog from Mac OS X when coecting to the 2.4GHz band: mac_syslog_2.4GHz.txt
Syslog from Mac OS X when coecting to the 5GHz band: mac_syslog_5GHz.txt
Syslog from OpenWRT when coecting to the 2.4GHz band: openwrt_mac_2.4GHz.txt
Syslog from OpenWRT when coecting to the 5GHz band: openwrt_mac_5GHz.txt