出错的INCAR
SYSTEM = C2H3
ISTART = 0

ICHARG = 2
ISPIN = 2
PREC = Normal
ENCUT = 520
LREAL = Auto

ALGO = Normal
ISMEAR = 0
SIGMA = 0.01

EDIFF = 1E-05
EDIFFG = -0.05
NSW = 300
NELM = 100

ISIF = 2
LORBIT = 11
NCORE = 12
NELECT = 1504

IBRION = 3
POTIM = 0
IOPT = 3
ICHAIN = 0

LCLIMB = .TRUE.
LCHARG = .FALSE.
LWAVE = .FALSE.
SPRING = -5

IMAGES = 4

IMAGES = 3

解决方法：
将 NELECT 注释掉。

官网上：NELECT sets the number of electrons.
Usually you should not set this line. The number of electrons is determined automatically from the POTCAR (ZVAL of the element) and POSCAR file (number of the atoms of the respective atom type).