ARC didn't find a correct conformer for a singlet carbene species

[alongd]

The species is:

Smiles: CCCC=CC[C]C=O
adjlist:

    1  O u0 p2 c0 {8,D}
    2  C u0 p0 c0 {3,S} {5,S} {10,S} {11,S}
    3  C u0 p0 c0 {2,S} {6,S} {12,S} {13,S}
    4  C u0 p0 c0 {7,S} {9,S} {14,S} {15,S}
    5  C u0 p0 c0 {2,S} {16,S} {17,S} {18,S}
    6  C u0 p0 c0 {3,S} {7,D} {19,S}
    7  C u0 p0 c0 {4,S} {6,D} {20,S}
    8  C u0 p0 c0 {1,D} {9,S} {21,S}
    9  C u0 p1 c0 {4,S} {8,S}
    10 H u0 p0 c0 {2,S}
    11 H u0 p0 c0 {2,S}
    12 H u0 p0 c0 {3,S}
    13 H u0 p0 c0 {3,S}
    14 H u0 p0 c0 {4,S}
    15 H u0 p0 c0 {4,S}
    16 H u0 p0 c0 {5,S}
    17 H u0 p0 c0 {5,S}
    18 H u0 p0 c0 {5,S}
    19 H u0 p0 c0 {6,S}
    20 H u0 p0 c0 {7,S}
    21 H u0 p0 c0 {8,S}

We expected to get a linear geometry:

But got:

O       1.35356100   -2.04187600   -0.27751400
C      -1.66813300   -0.61628700    0.36007000
C      -0.88428900    0.26015900   -0.62633800
C       2.50264900    1.51850400    0.21895400
C      -2.89996100   -1.26465400   -0.27629700
C       0.29557000    0.96714800    0.01116200
C       1.45071300    1.42849700   -0.82461700
C       2.07072500   -1.07058000   -0.16582800
C       1.63488300    0.28123000    0.16956100
H      -1.97601000   -0.00811600    1.21948400
H      -0.99715000   -1.39131700    0.73916300
H      -0.53981600   -0.35715300   -1.46151200
H      -1.55178600    1.02271800   -1.04707500
H       2.35964100    2.19995200    1.05689000
H       3.53495600    1.41092800   -0.10274500
H      -3.43976800   -1.88219100    0.44642200
H      -2.61580000   -1.90890700   -1.11384300
H      -3.59778100   -0.51151900   -0.65688400
H       0.02304000    1.62941700    0.83723200
H       1.57229400    1.34849200   -1.89467900
H       3.17073700   -1.15771700   -0.31276600

which looks like this: