Looks like this is breaking tools calling docutil too, e.g. https://bugs.launchpad.net/doc8/+bug/1837515 (fails on Python 2.7 but worked on Python 3 - possibly with some other package version differences)
Problem persists in the latest release, mrFAST v2.6.0.2, although now the SAM output...
uninitialized use of ret variable in Output.c