Since this is the thread linked on the Rock64 page with "In case you face stability issues, check this", I'm posting my issue experience and different workaround here.
After getting pretty consistent freezing even while idle on my 1GB Rock64 board I flashed the SPI to enable USB boot and switched to booting from external SSD drive rather than SD card and it has completely cleared up my freezing issues while also giving a huge performance/storage boost.
The board has been able achieve a stable uptime of over 60 days, now only intentionally going down for power losses or updates. Reverting back to booting from SD card immediately brings back the random freezing issues and occurs with multiple known good high quality cards from Samsung & Sandisk. I've maintained this no-SD card / USB boot stability through several upgrades since July 2020, current stable set up is Focal 5.9.14-rockchip64.
I don't know if there is a relationship between the higher memory speed and SD card access causing the issue as I never tried under-clocking the memory or if this is a separate issue altogether, but for those experiencing stability issues this might fix it for you as well while adding some performance rather than taking it away.
Ref:
Ayufan SPI flash to enable USB boot - https://github.com/ayufan-rock64/linux-build/blob/master/recipes/flash-spi.md
