weird solver behavior in rare cases

Dear,

I am using Gurobi-py to solve an LP problem about networks. I have tested my formulation on various network structures and different sizes of networks.

However, when testing on a specific network architecture (Regular random graph), the LP solver behaves abnormally and keep hanging for days, while I expect it to finish in a few hours.

The verbose output look like this:

Set parameter WLSAccessID
Set parameter WLSSecret
Set parameter LicenseID to value 2411299
Academic license 2411299 - for non-commercial use only - registered to 
Set parameter Threads to value 1
Set parameter Method to value 2
Gurobi Optimizer version 10.0.2 build v10.0.2rc0 (linux64)

CPU model: Intel(R) Xeon(R) CPU           E5645  @ 2.40GHz, instruction set [SSE2]
Thread count: 12 physical cores, 24 logical processors, using up to 24 threads

Academic license 2411299 - for non-commercial use only - registered to zi___@ugent.be
Optimize a model with 933744 rows, 10248547 columns and 30745638 nonzeros
Model fingerprint: 0xbc2a3413
Coefficient statistics:
  Matrix range     [1e+00, 2e+01]
  Objective range  [1e+00, 1e+00]
  Bounds range     [1e+00, 1e+00]
  RHS range        [1e+00, 1e+00]
Presolve removed 0 rows and 0 columns (presolve time = 5s) ...
Presolve removed 0 rows and 0 columns (presolve time = 12s) ...
...
Presolve removed 10584 rows and 1078 columns (presolve time = 65s) ...
Presolve removed 10584 rows and 1078 columns
Presolve time: 81.12s
Presolved: 923160 rows, 10247469 columns, 30534350 nonzeros

Ordering time: 1.75s

Barrier statistics:
 Dense cols : 1
 AA' NZ     : 2.531e+07
 Factor NZ  : 6.949e+08 (roughly 10.0 GB of memory)
 Factor Ops : 7.155e+11 (roughly 18 seconds per iteration)
 Threads    : 12

                  Objective                Residual
Iter       Primal          Dual         Primal    Dual     Compl     Time
   0   3.23639524e+04 -4.09898720e+06  9.51e+04 0.00e+00  2.76e+00   137s
   1   8.03768372e+04 -3.70949692e+06  1.84e-06 1.24e-07  1.85e-01   160s
   2   7.27224488e+04 -1.47985613e+03  2.16e-08 6.68e-17  3.62e-03   184s
   3   2.46246553e+03 -2.13034491e+02  5.29e-10 4.96e-18  1.31e-04   217s
   4   7.67216564e+02  2.65895752e+02  6.22e-10 6.54e-18  2.45e-05   254s
   5   5.24188026e+02  3.72928558e+02  2.08e-10 6.41e-18  7.38e-06   303s
   6   4.96584842e+02  4.54680256e+02  5.97e-09 6.52e-18  2.04e-06   349s
   7   4.75918787e+02  4.56386239e+02  7.93e-10 6.95e-18  9.53e-07   384s
   8   4.72676599e+02  4.72146454e+02  2.67e-12 7.22e-18  2.59e-08   418s
   9   4.72495362e+02  4.72495360e+02  1.89e-14 7.23e-18  1.18e-13   453s

Barrier solved model in 9 iterations and 453.23 seconds (195.01 work units)
Optimal objective 4.72495362e+02

Crossover log...

   55871 variables added to crossover basis                      460s
   56069 variables added to crossover basis                      465s
   56207 variables added to crossover basis                      471s
   56290 variables added to crossover basis                      475s
   56372 variables added to crossover basis                      480s
   56450 variables added to crossover basis                      486s
   56513 variables added to crossover basis                      491s

  866647 DPushes remaining with DInf 0.0000000e+00               493s
  192257 DPushes remaining with DInf 0.0000000e+00               609s
   36207 DPushes remaining with DInf 0.0000000e+00               642s
   10809 DPushes remaining with DInf 0.0000000e+00               649s
    2611 DPushes remaining with DInf 0.0000000e+00               652s
      76 DPushes remaining with DInf 0.0000000e+00               658s
      27 DPushes remaining with DInf 0.0000000e+00               688s
       0 DPushes remaining with DInf 0.0000000e+00               697s

   28166 PPushes remaining with PInf 0.0000000e+00               697s
   27774 PPushes remaining with PInf 0.0000000e+00               700s
Warning: 1 variables dropped from basis

Restart crossover...

  868473 variables added to crossover basis                      706s

  866647 DPushes remaining with DInf 0.0000000e+00               742s
  192257 DPushes remaining with DInf 0.0000000e+00               882s
   36207 DPushes remaining with DInf 0.0000000e+00               919s
   10813 DPushes remaining with DInf 0.0000000e+00               927s
    2613 DPushes remaining with DInf 0.0000000e+00               931s
       0 DPushes remaining with DInf 0.0000000e+00               957s

   28166 PPushes remaining with PInf 0.0000000e+00               957s
   27379 PPushes remaining with PInf 0.0000000e+00               961s
   26359 PPushes remaining with PInf 0.0000000e+00               965s
   25099 PPushes remaining with PInf 0.0000000e+00               970s
   23860 PPushes remaining with PInf 0.0000000e+00               975s
Warning: 1 variables dropped from basis
   22653 PPushes remaining with PInf 3.1530660e+03               981s
   21546 PPushes remaining with PInf 2.4795603e+03               986s
   20449 PPushes remaining with PInf 2.0880475e+03               990s
   19349 PPushes remaining with PInf 1.8215035e+03               995s
   17981 PPushes remaining with PInf 1.5106147e+03              1001s
   16883 PPushes remaining with PInf 1.3114404e+03              1006s
   15792 PPushes remaining with PInf 1.1576514e+03              1011s
   14695 PPushes remaining with PInf 1.0423197e+03              1016s
   13611 PPushes remaining with PInf 9.5618069e+02              1021s
   12529 PPushes remaining with PInf 8.9049878e+02              1026s
   11448 PPushes remaining with PInf 8.2397066e+02              1030s
   10367 PPushes remaining with PInf 7.5830642e+02              1035s
    8744 PPushes remaining with PInf 6.5717831e+02              1041s
    7388 PPushes remaining with PInf 5.5776587e+02              1046s
    6034 PPushes remaining with PInf 4.3528867e+02              1051s
    4953 PPushes remaining with PInf 3.7721312e+02              1056s
    3851 PPushes remaining with PInf 3.2555379e+02              1060s
    2485 PPushes remaining with PInf 2.3740235e+02              1066s
    1389 PPushes remaining with PInf 1.5143484e+02              1071s
     293 PPushes remaining with PInf 6.7048558e+01              1076s
       0 PPushes remaining with PInf 5.4404453e+01              1078s

  Push phase complete: Pinf 5.4404453e+01, Dinf 5.7977744e-03   1079s

Iteration    Objective       Primal Inf.    Dual Inf.      Time
  894814    4.7249536e+02   0.000000e+00   5.797774e-03   1083s
  894921    4.7249536e+02   1.987774e+04   0.000000e+00   1139s
  895021    4.7249536e+02   9.664704e+03   0.000000e+00   1252s
  895121    4.7249536e+02   1.368610e+04   0.000000e+00   1356s
  895221    4.7249536e+02   1.018289e+04   0.000000e+00   1457s
....
  928341    4.7249703e+02   1.438019e+04   0.000000e+00  19285s
  928431    4.7249704e+02   5.937866e+03   0.000000e+00  19311s
  928511    4.7249704e+02   4.230388e+04   0.000000e+00  19336s
  928611    4.7249705e+02   3.132018e+04   0.000000e+00  19363s
  928671    4.7249705e+02   2.611747e+04   0.000000e+00  19391s

Do you have any idea what is wrong with this?

Best regards,

Z.