if I was you I would test out the following:
* Try a different power supply, especially if the one you are using is below a 3A rating.
* See if you can get a slower SD card to try. It seems to me that (at least with mainline) the Rock64 may have some trouble with some cards. Like I have some Samsung EVO cards that seem to have problems with the Rock64 but slower Patriot Class 10 ones work OK.
* Try a different power supply, especially if the one you are using is below a 3A rating.
* See if you can get a slower SD card to try. It seems to me that (at least with mainline) the Rock64 may have some trouble with some cards. Like I have some Samsung EVO cards that seem to have problems with the Rock64 but slower Patriot Class 10 ones work OK.