Joint following error on stepper system

You have resurrected a very old thread here. But the only reason that you can have a following-error with a stepper system is if the system simply can't emit enough steps to follow the requested velocity. This can be caused by step length too long or base thread too slow (if you are using software stepping)

You have a base thread of 100,000 ns so can step at 10kHz

The G-code line that causes the problem is well within the B-axis limits, but which axis is the f-error on? My guess is that (because of the 5axis kinematics) the B-move is requiring a very rapid move of another axis (faster than the system can generate steps) and that is triggering the f-error.

Unfortunately LinuxCNC does not know how to limit the speed of an axis that is inside its limits to keep an axis that is moving separately as a result of kinematics inside its limits.
(If both axes are commanded to move in the same G-code line then it limits to the slowest)

You could either limit the B-move to a speed that the other axes can follow, or possibly add a move of the dependent axes to that move so that their position in real space (rather than in TCP space) remains approximately constant)

I have long wished to fix this, I even think I know how, but have never found the time when it was near enough the top of the pile.

OK, so the X axis is trying to make a long, fast move to stay at the same position in TCP space, and can't quite follow fast enough.

If you convert that G0 to a high-feedrate G1 (or make the move with the tool closer to the work, if it is retracted) then it might work.

It's generally a good idea to give an update of what you have changed and what is (still) not working.
Looking at your hal and ini files it looks like you lowered the base thread and also lowered the angular joint maximum velocities. I presume you are still getting joint0 following errors when moving the B axis?. Also the pivot length setting seems to have disappeared?
Have you tried lowering the Baxis/joint velocities further?

You have set a max velocity of 25°/s for the angular B axis with a pivot length + tool length of say 100mm.
A command of G0 B25 will thus result in a TCP displacement in the x direction of tan(25)*100=46.6mm (ie the x-axis has a required velocity of at least 46.6mm/s )
This explains the joint0 following error since your joint0 has a max velocity of 25mm/s.
If your joint0 can really only go 25mm/s your B axis can only move as fast as:
0.8*atan(25/100)=11°/s (the factor 0.8 allows for 20% head room for step generation)
Note that this will decrease further if your pivot length + tool length is more than 100mm.

Similarly you would need to check the axis/joint max acceleration values.

[edit]
Of course the same goes for the other two (y,z) linear axis/joint velocities/accelerations and also the c angular axis/joint