Upgrade Guide suggestion
I suggest that the Upgrade Guide section "3.1 Changing architecture (32-bit to 64-bit or vice versa) during upgrade" be revised to include a step to confirm that the firmware updater settings are correctly configured after installing 64 bit and restoring the configuration from 32 bit.
About a month ago, I upgraded the hardware on which pfsense is installed. I was previously using 32 bit, but with the new hardware installed 64 bit. After installing 64 bit 2.2 release version on the new machine (current version at the time), I restored the configuration from the 32 bit server and all went smoothly. On Friday evening, I clicked the "Invoke Auto Upgrade" button. After the reboot, I noticed some errors in the pfsense GUI. Then I noticed that it had installed the 32 bit version.
I'm 99% sure the problem was caused when I installed the 64 bit version. Even though I had never changed the firmware updater settings, the configuration file from the 32 bit version has the 32 bit version updated address. And the configuration backup I made before the attempted auto upgrade also contained the address for the 32 bit updates.
I installed fresh again with the 64 bit 2.2.1 version and after restoring the configuration, found that the Firmware Auto Update URL was set to http://updates.pfsense.org/_updaters rather than https://updates.pfsense.org/_updaters/amd64