Per -> Apr 5 12:28:01 kernel: jffs2: Error garbage collecting node at 02d76b8c!
There's likely a bad NAND block which may be preventing the GC routines from working. This kicked my a$$ around the block and back with 384.18/19 on an AC86U. I'm sure this is discussed in that long thread about what we were seeing.
IMHO, a
@L&LD reset may be coming but you can also try this to save anything in the /JFFS:.
a) See if you can take a backup of the JFFS in GUI to save whatever. You may have to resort to copying files off individually as well.
b) Turn off the JFFS, reboot
c) Verify you have the latest firmware updates installed - which fixed a bad block = no format scenario, if not, install, reboot the router properly.
d) Turn on JFFS
e) reboot the router
f) Monitor the log closely.. you will see the format when booting and likely it will ID the bad block.
Longer discussion in here ->
https://www.snbforums.com/threads/asuswrt-merlin-384-19-is-now-available.65801/page-24#post-615444
The root problem is the NAND garbage collection needs larger contiguous free-space to do reclaim/compaction/trim... and when there's a bad block, that can cause that contiguous space to be too small. If the
format jffs on boot cannot "map around" the bad blocks during the format, then the problem will persist. The bad block will be added to a bad-block table by the format if all goes well. You may have to turn on "debug" in the logs to see those messages. Good Luck! Stay safe, stay alive! Peace.