Are you able to explore if there is plenty of free space for the download? I don’t know which would be the working directory but Chromium may download into some size limited space, perhaps.
The need for a good capacity data cable is often a problem but as your FP4 seems to have been identified the cable may be ok.
A Mac can also have problems with “unknown executables” – I have no knowledge to help on this though but it might account for the rather vague error.