When spacarlight (and also the full spacar) is called, it reads and writes an input and output file to the disc of your computer. Especially when spacar is called repeatedly in consecutive calls, this can cause read/write errors which can cause the simulation to fail or matlab to crash (Fortran/intel read/write error).

To prevent this problem, make sure your working directory in matlab is not synchronized over the internet (in example an active dropbox folder or other cloud service). Best practice is to use the C: disk.