I have the same problem, with Orange Pi PC Plus, which worked just fine for a day (with several reboots) - until I booted it the next day

Happened twice already, with two different SD cards, one Kingston, and one Sandisk.
Symptoms: once the Dietpi folder was completely empty, once there were enough files (apparently) missing to mess up the system and prevent services from starting (squeezelite & Logitech Media Server).
Once it happened after an update, but the other time I did not do any updates, just installed LMS and Squeezelite and rebooted 2-3 times, all was well, until on 4th reboot the services wouldn't start, with the usual symptoms.
The power supply is ample (5V/3A), and works just fine...
Sorry, can't provide more info, blanked the sd cards already, and waiting to see if there are any suggestions....
BTW, thanks for the wonderful distro and all the good work!