Many moons ago I learned that there is a limit like max 25 nm out for the LOC and 17 nm for the GS. This is imho the earliest where you can receive reliable signals. I experienced something similar on the 747 as well but if you keep your hand on yoke and thrustlevers you just switch the damn A/P of instead of watching it trying to kill you.
If you don t understand the automatica at any moment revert to manual flying
