'wget returned 4' when updating package lists

I've been noticing that occasionally when I am attempting to find/install a package (either via luci or opkg directly) that there will be a problem updating the package lists. Right now I'm seeing:

# opkg update
Downloading http://downloads.openwrt.org/releases/18.06.1/targets/mvebu/cortexa9/packages/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_core
Downloading http://downloads.openwrt.org/releases/18.06.1/targets/mvebu/cortexa9/packages/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/18.06.1/packages/arm_cortex-a9_vfpv3/base/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_base
Downloading http://downloads.openwrt.org/releases/18.06.1/packages/arm_cortex-a9_vfpv3/base/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/18.06.1/packages/arm_cortex-a9_vfpv3/luci/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_luci
Downloading http://downloads.openwrt.org/releases/18.06.1/packages/arm_cortex-a9_vfpv3/luci/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/18.06.1/packages/arm_cortex-a9_vfpv3/packages/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_packages
Downloading http://downloads.openwrt.org/releases/18.06.1/packages/arm_cortex-a9_vfpv3/packages/Packages.sig
Signature file download failed.
Remove wrong Signature file.
Downloading http://downloads.openwrt.org/releases/18.06.1/packages/arm_cortex-a9_vfpv3/routing/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_routing
Downloading http://downloads.openwrt.org/releases/18.06.1/packages/arm_cortex-a9_vfpv3/routing/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/18.06.1/packages/arm_cortex-a9_vfpv3/telephony/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_telephony
Downloading http://downloads.openwrt.org/releases/18.06.1/packages/arm_cortex-a9_vfpv3/telephony/Packages.sig
Signature check passed.
Collected errors:
 * opkg_download: Failed to download http://downloads.openwrt.org/releases/18.06.1/packages/arm_cortex-a9_vfpv3/packages/Packages.sig, wget returned 4.
 * opkg_download: Check your network settings and connectivity.

My network connectivity has been rock solid and right now (i.e. I've tried a few times in the last 15 min) it seems to be having a problem with the packages... err... packages. Any idea what's going on?


@vgaetera thanks... I was able to find a different post talking about a network problem but since I was able to manually wget it without problems was thinking that wasn't it. However, the link re: ipv6 failure looks like what I'm running into (i.e. when I wget it from a PC, the ipv6 fails so it falls back to ipv4 which works... guessing the router wget isn't doing that) Strange that it's only that one file... I'd expect them all to fail since they're on the same host.

DNS-reply could vary if some DNS-server answers faster or slower than others.
Also while some applications could send several DNS-requests and report failure only if all the requests fail, some others report failure after the first failed DNS-request.

Where did this DNS theory materialize? As downloads are all from the same host, the router has the address in its cache since the first query.

In that case better run tcpdump and investigate the traffic.