Need help to test XY motors

Hi,
I‘m testing XY axis motors on my new DIY printer.
Hardware - RAMPS 1.4 and Arduino Mega 2560.
I disabled microsteping at all, changed DEFAULT_AXIS_STEPS_PER_UNIT to 10 assuming that every instruction to move axis by 0.1mm will give one full step. However, controller skips first five instructions to move by 0.1 mm and after the sixth instructions received, it generates six impulses at once.
What parameters I should change to avoid such strange behavior?


Admin: Below added at request of author:

I recorded small video to describe my problem. Please switch to HD, look at Y position and motor movements.

[youtu.be]

Any ideas?