Random errors through multi-threading in GHPython

Hi,

I made a script to calculate "C-Values" (i.e. viewing quality of each seat) in a stadium bowl. It was running slow so I rewrote it using the parallel module, which greatly sped things up.

Unfortunately, every now and then I randomly get an error message when changing parameters or even just clicking "Test" numerous times in the GHPython editor (see attached pic):

Runtime error (AggregateException): Mindestens ein Fehler ist aufgetreten.
Traceback: 

line 27, in run, "C:\Users\Michel\AppData\Roaming\McNeel\Rhinoceros\5.0\Plugins\IronPython (814d908a-e25c-493d-97e9-ee3861957f49)\settings\lib\ghpythonlib\parallel.py"
line 57, in script

The German sentence means "At least one error has occurred."

Attached is a dumbed down version of the script. The problem occurs more often when I use the actualdefinition (which includes a bunch of other GHPython components).

Any help much appreciated!

Cheers,

Max