Please help with PTR 4300

The printer moves the balancers correctly, loads the plate without error. When it spins the drum to expose, after a few turns it gives error E415b - The balancer is not moved to the target position.

Sounds like as it spins up it doing one of the following
A) Balancer weights are moving or B) It can not see the balancer weights.

Things you do, check if the balancer weights are moving by them self, if you rotate the drum round manually see if they move, or if you touch a weight see if it moves much.

clean the flag of the balancer weights (home tends to get dirty quicker) sometimes using some fine sand paper on the flag to make it shiny can help, as can cleaning the sensors

Take out balancer blocks.
Clean with IPA as marked on attached image.
If no improvement, check black gum stoppers for wear, if worn just replace rubber pieces. No need to replace whole balancer blocks.
Error have nothing to do with balancer flag or sensors.
Chris

One thing that you can, do is mark on the side of the drum the position of the weights its a bit rough, but should show any major movement, try to recreate the error, if they have moved then as others have said cleaning can help, but if they have not moved, you need to look at other things. Rather the markings you can use the balancer test to find the current position before and after the error as an alternative, this is more accurate

The error does very much have to do with flag and sensors as the machine only knows where the balancer weights are on the drum via the flag and sensor. If the weights have moved when they should not, it is known via the flag and sensor. Equally if the sensor can not see the flag when it spins at high speed you can get errors. Sometimes the sensors are OK at normal load time / balancer change time, but during high speed drum rotation can error, it is less common, but can happen if sensors are just on the borderline of reading the flag

Blocks are moving during drum spin. No other cause.
Chris