Best as I can determine, this problem has gone away once I have corrected the Caddyfile and actually completely restarted Caddy.
I do not know what iterations of incorrectly structured Caddy files I had reloaded. I feel something during reloads did not clear correctly and caused this intermittent problem.
I added a log directive. However, that directive will only take affect on the start of Caddy, not a reload.