I encountered a bug when generating From header fields when there is a word that's longer than the maxLineLength parameter. The problem is that relay::generate calls text::generate with text::FORCE_NO_ENCODING, which gets passed to word::generate. Now, if encoding is not needed, it does the line length checks and calls the recursion on line 392. Then, in the next recursion, on line 340 encodingNeeded is set to true on line 340, and then set to false again on line 345 since the FORCE_NO_ENDCODING flag is enabled. Because of this, the recursion is entered again, etc etc.
The workaround is to use a larger line length, but this does not seem very robust - the From fields are set by random hosts along the way and can hold any arbitrary value, which shouldn't be modified and can't really be controlled.
Let me know if you want me to open a bug about this.