I think you understood me wrong, or maybe I wrote not clear enough.
The DM556 driver can easily work with 64 and 128 microsteps. As I should set a number of microsteps for the GoTo lower than for the tracking, I set 128 for tracking and 64 (or lower) for GoTo. But when the slew begins, it seems to work properly only within an acceleration, then runs twice slower. I assume that its twice slower, because the final position is in a half of the way.
I know a behaviour of the stepper motors in general, if I want to do same way using a twice lower number of microsteps, I have to also lower twice the number of steps. But if the number of steps is lower while the setting is still 128, then the way is twice shorter.
I don't understand this feature, to be honest, but I think that my drivers cannot use it. So I have to switch the GoTo microsteps off, then everything works.