Extra slow steps at the end of a move

Hi all,
my motors makes some strange extra steps (don’t know if they are necessary to complete my move, or just extra garbage), VERY slowly, at the end of deceleration ramp. Searching in grbl form I found a similar issue (#139).
Don’t think is a Planner issue, as I send simple straight move instructions (G0 Y20 F5000, pause, G0 Y-20 F5000, and again)
Something related with acceleration/deceleration curves in conjunction with an unlucky parameter combination ?

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