[MM3-users] Importing mbox files into archive defect with lines with From

A curious problem, but seems to be well defined. I am importing mbox format files with 25 years worth of archives in 250 files from a Listserv list into hyperkitty. All is going swimmingly, except I get lots of partial emails with sender of None put into the current month, with text that has clearly been truncated. As I look at each one, I see that the line in the imported text is immediately after a line starting with 'From'. Clearly, 'From:' is an RCS-82 header, but 'From ' is not, and yet there is much evidence here that this is messing up the import.

Is this a known bug? If not, how do I report it?