After repairing the spindle, our machine doesn't change tools anymore.

Machine just runs in manual- and automatic-run up to reference point Z-axis.
In manual-run we get the error report: ''500 end position Z-axis''.
In automatic-run an inherited error without error description is shown by LED.
Spindle has been referenced to position. Spindle works!
With a special key combination we were able to break the reference point while starting the controller - and so we could change tools in manual-run. Mechanically everything is okay.
Even if the spindleis in tool-change-position the tool changer doesn't respond to any control command or key function.

Anybody here with the same problem? We need help.
Machine has to be stopped and our customers wait for the orders.