If udhcpc fails to get dhcp lease you're stuck on boot forever
If you have wpa_supplicant configure on wlan0 and for some reason if fails to get a DHCP lease, it will keep trying. Forever. You’re stuck on it and can never reach tty. Hard reboot needed.
If wpa_supplicant fails to get a lease it should try 1 or 2 more times only. Not forever.
(from redmine: issue id 6705, created on 2017-01-19, closed on 2019-05-06)