Hello. Recently I installed factory image on my WRT1200AC again and had unstable internet for simingly no reason. Random web pages didn't load at all and few seconds/minutes later they did... This was going on in an endless loop. Default configuration with minor modifications worked fine for me previously for many years. After looking for a solution I found this post and it look promising:
However, attempting that a few times resulted in some networking misconfiguration that forced me to reinstall image, as webgui and ssh were not accessible. Eventually I noticed this line 'uci del network.lan.netmask' before applying changes in webgui:
# /etc/config/dhcp
uci set dhcp.lan.ra_management='1'
# /etc/config/network
uci del network.lan.netmask <-- netmask to be removed
uci set network.lan.broadcast='10.10.10.255'
uci set network.lan.gateway='192.198.1.4'
uci add_list network.lan.dns='1.1.1.1'
uci del network.lan.ipaddr
uci add_list network.lan.ipaddr='10.10.10.1'
Looks like not having netmask messed up my config. Adding all config lines manually and rebooting router solved my issue.
Hope this helps someone