Unfortunately, there's a lot of misleading information on the watchdog timer..in part because the device and kernal modules have changed between models of Pi and versions of Raspbian. I found the information I needed to get them going here...
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Paradroyd (paradroyd@mastodon.sdf.org)'s status on Friday, 09-Aug-2019 23:31:46 UTC Paradroyd - Stephen Michael Kellat repeated this.
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Paradroyd (paradroyd@mastodon.sdf.org)'s status on Friday, 09-Aug-2019 23:48:14 UTC Paradroyd I also found some good info on the watchdog timer here, but the info here is from 2013, so you have to keep in mind that some of the device / driver names have changed.
http://blog.ricardoarturocabral.com/2013/01/auto-reboot-hung-raspberry-pi-using-on.html
Stephen Michael Kellat repeated this.