How much do you use the link? Got any big regular uploads/downloads going? Either that is a heavily used line or there is an issue somewhere. Can you post the stats from the router for SNR/margin/attenuation and if possible any error stats.
Nope, no big uploads or downloads - a Nest Hello Doorbell, but this has been like this before it was installed. Kids use their phones when not at school, but even during the day (when they're at school) it still seems to be quite high.
Is this below what you're looking for?
Noise margin (up/down) 5.9/10.1
Line attenuation (up/down) 23.9/23.7
Signal attenuation (up/down) 23.8/21.2