I have had a similar experience with NetworkManager.
The solution was to set a fixed IP.
All problems solved!
Some history.
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My Orange PI PC was running an old Armbian 5.11 (Debian 8.11).
Had been running rock sold since installation date, with a fixed IP.
A WD 500GB SATA disk is attached (USB docking station: JMicron, JMS579) to store files (approx. 50 GB/day).
I did a fresh install: "Armbian 20.05.2 Orangepipc Debian buster" with DHCP enabled (IP reservation on the router).
Result: random halting of the system (runs headless in a remote location).
Sometimes after an hour, sometimes after a few hours, sometimes a bit longer.
Even checksums of the files were sometimes (1 à 2%) calculated wrong!
Files got sometimes corrupted (5-10%) when transferred over the wired connection.
Recent syslog etc were missing when the system halted.
Installing watchdog was not a real solution of course but would most of the time reboot the system (not always).
Setting a fixed IP solved all the problems.
The Orange PI PC was and is running at max 1008MHz (SoC runs between 480 and 1008MHz using conservative governor).
I also installed a fan to keep things cooler: max 54°C under full load (stress @ 4cpus).
But this did not solve the problems.
Only setting a fixed IP solved al other issues.