And it (flashing to latest firmware) is recommended for all Ant devices as far as I know.
Perhaps recommended by Bitmain, but NOT recommended by us users!
Flashing to latest firmware is always a last-resort move.
As the saying goes, " If it ain't broke... " but in this case, yes, flashing to latest is the next step.
opkg is not Bitmain
https://wiki.openwrt.org/doc/techref/opkgUpgrading packages is generally
NOT recommended for most users, because a typical OpenWrt system stores the base system in a read-only SquashFS partition.
We can try at least there are no other way to solve it.
How can I flash a firmware through SSH ?
Nice question ) Possible but quite complex.
Can you run
/usr/sbin/lighttpd-angel -f /etc/lighttpd.conf