@Igor regarding zram , i just got some errors visible in dmesg after a day or so of the board being idle
root@odroidn2:/home/juanjo# uname -a
Linux odroidn2 4.9.179-odroidn2 #17 SMP PREEMPT Tue May 28 22:32:11 CEST 2019 aarch64 aarch64 aarch64 GNU/Linux
[43913.709044] zram: Decompression failed! err=-22, page=12681
[43913.709066] zram: Decompression failed! err=-22, page=12681
[43913.709080] zram: Decompression failed! err=-22, page=12681
[43913.709086] Buffer I/O error on dev zram0, logical block 12681, async page read
if you want i can do some sort of testing on it. my knowledge on kernels and this kind of stuff is minimal but if i can be of any help let me know.