multi-axis (angular/linear) joint following error - single axis ok

So - i am adding a 4th axis to my lathe/mill. when i test the x & z axis (linear) both separately and together i do not get any joint following errors (steppers using mesa 7i76).
I added a rotational axis and it tests fine in isolation and when i am doing slow moves (G1 B10 X200 Z150 F100) i do not get following errors - but with rabids or faster moves (G1 B10 X200 Z150 F1500) i am getting joint following errors on the linear axis (sometimes X sometimes z).
It does not seem to respect the max velocity settings in either axis or traj sections when doing a move combined with angular and linear.

I am running LinuxCNC 2.7.8

I have read that running halscope should identify the issue but i don't know what to look at.
Any suggestions?

Yes- it was 5axiskins related - so i am utilizing the W axis to store the TLO - after a tool change a G0 W0 will then have the TP run through the kins changes needed to "implement" the proper TLO and related other axis changes.