Be confused during the stacking fault energy calculation

[zyang]

hi, everyone.
Recently, I did some stacking fault energy calculations with the CINEB method. During the calculation, the atom positions in x and y directions were fixed, in z directions were fully relaxed. However, the obtained stacking energy curve is not a smooth line, it's a bit like a stepped shape. This is not consistent with the reported in other's literature. Is there something wrong?
Here are my INCAR and POSCAR, the attachment is my obtained mep fingure
I am INCAR:
SYSTEM = neb_11-2
ENCUT = 500
EDIFF = 1e-6
#EDIFFG =1e-4
EDIFFG =-0.05
PREC = High
NSW =150
ISIF = 2
ISTART=1; ICHARG=1
ISMEAR = 1; SIGMA=0.05
#No writing charge density and wavefunction
LCHARG = FALSE
LWAVE = FALSE
#Target Pressure
PSTRESS = 0
#Finer optimization
#Parallelisation
NPAR = 6
ISYM= 0
# NEB
IOPT=1 #Optimizer QM=Quick-Min
IMAGES=5
SPRING=-5
IBRION=3
POTIM=0
ICHAIN=0 #Indicates which method to run. NEB (ICHAIN=0) is the default
LCLIMB=.TURE.

And I am POSCAR:
Diamond
1.00000000000000
2.4996954420617001 -0.0000015984273025 -0.0000004288426044
-1.2498615966422699 2.1647917406915802 0.0000004267270135
-0.0000743380333258 0.0000428738641867 46.0935034566772970
32
Selective dynamics
Direct
0.3333333049357490 0.6666660697493049 0.0021366781793901 F F F
0.3333321176947545 0.6666667076499110 0.1321074681009725 F F T
0.3333321338100439 0.6666659187804977 0.2647965727786683 F F T
0.6111093303710505 0.3888874016608069 0.3988126873320129 F F T
0.6111093721998483 0.3888864056046651 0.5316088751402823 F F T
0.6111097208958861 0.3888864932070802 0.6670575131577106 F F T
0.6666644646826403 0.3333346031683767 0.0438434388119439 F F T
0.6666656024293933 0.3333329075687740 0.1763847966237373 F F T
0.6666651979090841 0.3333323733849654 0.3092564409585279 F F T
0.9444426319744587 0.0555537086208867 0.4430573547638433 F F T
0.9444431467093198 0.0555525797801807 0.5759200401383540 F F T
0.9999984870075579 0.0000004794387020 0.0878462672246497 F F T
0.9999990252937281 0.9999992318772236 0.2206452355765917 F F T
0.2777764063445483 0.7222207712816288 0.3545988134402662 F F T
0.2777760106917957 0.7222200258261842 0.4873279199653310 F F T
0.2777770807104186 0.7222187795122732 0.6204568019188548 F F T
0.3333318400641144 0.6666670986152501 0.0988517225959876 F F T
0.3333321367439461 0.6666661118582257 0.2317050154148473 F F T
0.6111094010157905 0.3888877768560582 0.3657260093063288 F F T
0.6111090858581146 0.3888869599267734 0.4983939738538517 F F T
0.6111104717286274 0.3888853639133751 0.6309276850293514 F F T
0.9999978611093711 0.0000011654767655 0.0543135352870216 F F T
0.9999986989533488 0.9999997559849576 0.1874524659483303 F F T
0.2777763128821476 0.7222211576011309 0.3212712939962432 F F T
0.2777757328210865 0.7222206096787445 0.4541232295603092 F F T
0.2777765499622237 0.7222192594891580 0.5869240009236529 F F T
0.6666651292474839 0.3333342556319181 0.0077107723184398 F F F
0.6666653748951629 0.3333333998073126 0.1431676784270430 F F T
0.6666652157921974 0.3333327812184105 0.2759265438885297 F F T
0.9444425230264414 0.0555542978116273 0.4098715352145952 F F T
0.9444426823062695 0.0555532409134226 0.5426666680412003 F F T
0.9444419886078893 0.0555542082653500 0.6726617278170499 F F T