* What led up to the situation?

     Checking for defects with

[test-]groff -mandoc -t -K utf8 -rF0 -rHY=0 -ww -b -z < "man page"

  [test-groff is a script in the repository for "groff"] (local copy and
"troff" slightly changed by me).

   * What was the outcome of this action?

troff: backtrace: file '<stdin>':80
troff:<stdin>:80: warning: trailing space in the line

   * What outcome did you expect instead?

     No output (no warnings).

-.-

  General remarks and further material (declared as a "diff" file) are in the
attachments.