scf convergence fails for Uranium based coordination compounds


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Hi. I am trying to run a series of calculations on different uranium based coordination compounds, but I got all of them failing- the scf cycle does not converge

I am copying my input file

GEOMETRY
H    -7.232548    -2.275358     0.486014
C -6.492637 -2.338257 1.270217
C -5.497566 -3.323589 0.914568
C -4.261059 -3.510227 1.476223
O -3.832645 -2.851531 2.511246
U -5.071889 -2.454629 4.342482
N -3.643535 -3.269865 6.316560
C -2.706916 -4.327936 6.039378
N -6.500162 -1.639181 2.368390
C -7.436677 -0.581028 2.645611
O -5.978969 -3.919024 4.113230
O -4.164847 -0.990206 4.571715
O -6.311160 -2.057728 6.173702
C -5.882773 -1.398936 7.208675
C -4.646227 -1.585437 7.770299
C -3.651084 -2.570705 7.414682
H -3.553654 -4.202668 1.044363
H -6.590210 -0.706504 7.640498
H -2.911097 -2.633428 8.198828
H -5.714970 -3.878461 0.004695
H -4.428820 -1.030466 8.680109
H -7.977207 -0.326872 1.735034
H -8.142378 -0.910972 3.406560
H -6.898684 0.294988 3.004888
H -2.915897 -4.749701 5.057360
H -1.693684 -3.929138 6.055021
H -2.802846 -5.105133 6.796137
end

BASIS "ao basis" PRINT
U Library "Stuttgart RSC 1997 ECP"
H Library cc-pVDZ
C Library cc-pVDZ
O Library cc-pVDZ
N Library cc-pVDZ
END

CHARGE 0

DPLOT
SPIN spindens
END

scf
direct filesize 100000000
singlet
end

RELATIVISTIC
ZORA
END

DFT
xc pbe96
iterations 500
convergence energy 1e-6 density 1e-5
smear 1
grid fine
mulliken
end

TASK dft optimize
task dft freq


I have tried with and without smear, fine and xfine grid and changing the convergence criteria for energy and density. In all cases, the SCF behaves like this

  convergence    iter        energy       DeltaE   RMS-Dens  Diis-err    time
---------------- ----- ----------------- --------- --------- --------- ------
d= 0,ls=0.0,diis 1 -8641.0811366797 -1.14D+04 6.27D+00 1.13D+02 438.2
Grid integrated density: 198.001640727949
Requested integration accuracy: 0.10E-06
sigma= .10D+01 eFermi= -1.22871 T*S= -4.56E+01 nel(1)= 198.00 nel(
d= 0,ls=0.0,diis 2 -8339.8792074782 3.01D+02 6.48D+00 3.94D+02 560.1
Grid integrated density: 198.000395016022
Requested integration accuracy: 0.10E-06
sigma= .10D+01 eFermi= -1.11165 T*S= -5.67E+01 nel(1)= 198.00 nel(
d= 0,ls=0.0,diis 3 -8578.2631970768 -2.38D+02 1.32D+00 1.07D+02 687.6

**************
Requested integration accuracy: 0.10E-06
sigma= .10D+01 eFermi= -0.96883 T*S= -6.04E+01 nel(1)=  198.00 nel(
d= 0,ls=0.0,diis 498 -8631.7121867927 6.15D-03 1.09D-03 1.79D+00 62222.7
Grid integrated density: 198.000545774563
Requested integration accuracy: 0.10E-06
sigma= .10D+01 eFermi= -0.96862 T*S= -6.04E+01 nel(1)= 198.00 nel(
d= 0,ls=0.0,diis 499 -8631.7236499945 -1.15D-02 9.17D-04 1.79D+00 62348.8
Grid integrated density: 198.000545975440

Any idea how I could get convergence?