What is this error indicating - The task tries to instantiate a sub-process with depth greater than the limit of 100

As the error message says: the maximum "depth" of subprocess calls (from the top-most parent) is 100.  The only time I've run into this myself was when I was using a system of recursively invoking new instances of the original top-level process to avoid having to do too much looping in the design (which, to be fair, worked well until one particular instance pushed the depth over 100).

As the error message says: the maximum "depth" of subprocess calls (from the top-most parent) is 100.  The only time I've run into this myself was when I was using a system of recursively invoking new instances of the original top-level process to avoid having to do too much looping in the design (which, to be fair, worked well until one particular instance pushed the depth over 100).