RT-N16 frequently crashing/rebooting after upgrading to 18.06.2

I own an ASUS RT-N16 router which was previously running either 15.05 or 15.05.1 (don't remember which.) I recently upgraded to 18.06.2, as well as added a DMZ. For the past day or two my router has been rebooting a lot. I'm not sure exactly what triggers it, but it seems to happen more often when I'm doing data transfers. I honestly have no idea how to go about troubleshooting this. Is there a crash log I can take a look at?

after such crash reboot from the ssh cli cat /sys/kernel/debug/crashlog

OK, here is the latest crashlog: https://gist.github.com/kyleedwardsny/228a6788c92104342e16fa9d5881156c

It looks like this one was in the b43 module, and had something to do with hostapd. I will keep checking the crashlog and see if this happens consistently.

Hmm, this is weird... after the latest crash, /sys/kernel/debug/crashlog doesn't exist.