If anyone has problems with the CNC shield v4 to be used together with GRBL (at least v 1.1f) have a look at the video i made..
It explaines the problem, and solution.
This board design is totally fu**ed up, there are exchanged STEP - DIR pins, but most problem that jumpers for A4988 are made for GND instead of Vcc (5V) . So to fix STEP DIR simply compile GRBL with proper pins defined or modify the board by some traces cuts and some shortcuts. Most important is to modify jumpers by adding pull-up resistors about 4k7 for proper set of micro stepping of motor, elsewhere the motor will loose steps in full step mode, or be working very slowly.