7th Axis Coordinated Motion Robot Lagging

I have a IRB 4600-45/2.05 with an MU100 ext axis and 50:1 gearbox.

We are seeing overshooting/ lag when performing coordinated motion.

We have done tuning on the axis with no improvement

I have attached a video of the robot following 20 degrees of motion (of the 7th).

At slower speeds in manual the lag is barely present.

When we go into auto we see <1-2mm drift.

Any help would be greatly appreciated.

Yes gear ratio is good through full rotation.

TCP holds accurately through 40 degrees coordinated motion

Quote from hermann

Think it's a matter of not optimized control parameters. If the P part of controller parameter differ too much you will get that kind of lags.

Sorry, yes you were correct, parameter tuning was required