so much can go wrong - and I'm far from an expert with the 24t but I'll try to describe the annoying problem I just had with one since I don't think I saw it explained here - it'll at least give you something else to check.
The "tucker fingers" - if I'm calling them the right thing - two of them, one for each knotter - big cam-shaped flat metal disks that lie flat under the knotters...
Those are controlled by rods that are attached to a bracket that swings forward every time the knotters cycle.
On this 24t - the sheet metal of the bale chamber itself occassionally gets forced upwards by the pressure of the hay in the chamber. So much so that it eventually interferes with the metal arms that swing and push the rods for the tucker fingers.
It usually results in half-knots that just fall apart.
It's fixed by slamming the whole area down repeatedly with a heavy hammer and a large flat punch - to push the sheet metal out of the way so they don't bind.