if your z motors are connected to m5 rods
#define DEFAULT_MAX_FEEDRATE {300, 300, 5, 25} // (mm/sec)
is two fast for them
change to
#define DEFAULT_MAX_FEEDRATE {300, 300, 2, 25} // (mm/sec)
some can get away with 3.
#define DEFAULT_MAX_FEEDRATE {300, 300, 5, 25} // (mm/sec)
is two fast for them
change to
#define DEFAULT_MAX_FEEDRATE {300, 300, 2, 25} // (mm/sec)
some can get away with 3.