forrtl: error (65): floating invalid. MODFLOW-6 simulation error related to DISV package

[jarmodevries]

Dear community

I'm trying to run a MODFLOW model in FloPy using an unstructured grid I constructed in ArcGIS Pro.
I've imported this grid as a shapefile. Extracting polygon coordinates from the shapefile, I wrote a DISV package, without any errors. Here's a plot showing part of the grid:

Writing the other packages also went well: it all gives input files which seem to look okay.

When running the entire simulation, I get this error:

MODFLOW runs in SEQUENTIAL mode
 
 Run start date and time (yyyy/mm/dd hh:mm:ss): 2024/12/19 14:13:51
 

 Writing simulation list file: mfsim.lst
 Using Simulation name file: mfsim.nam
 
forrtl: error (65): floating invalid
Image              PC                Routine            Line        Source             
mf6.exe            00007FF6432EF20A  DISVGEOM_mp_CPROP         193  DisvGeom.f90
mf6.exe            00007FF643296135  CONNECTIONSMODULE         804  Connections.f90
mf6.exe            00007FF6432D3CDE  DISVMODULE_mp_CON         696  Disv.f90
mf6.exe            00007FF6432D249B  DISVMODULE_mp_GRI         511  Disv.f90
mf6.exe            00007FF64349195F  GWFMODULE_mp_GWF_         228  gwf.f90
mf6.exe            00007FF6435A1E4C  MF6COREMODULE_mp_         318  mf6core.f90
mf6.exe            00007FF64359E0CB  MF6COREMODULE_mp_          43  mf6core.f90
mf6.exe            00007FF64359DDB2  MAIN__                     11  mf6.f90
mf6.exe            00007FF6437D956E  Unknown               Unknown  Unknown
mf6.exe            00007FF6437D9950  Unknown               Unknown  Unknown
KERNEL32.DLL       00007FFBF0747374  Unknown               Unknown  Unknown
ntdll.dll          00007FFBF211CC91  Unknown               Unknown  Unknown
Model did not run successfully.

Does anyone know where this error comes from and if there are any ways to fix it? I suspect the error has something to do with the DISV package, but I checked the coordinates (possible duplicates?), cell areas, number of vertices, etc, and that all looks okay...