I think you are saying it occurs after you paste it into their platform, so I don't think a setting in Word or Wordperfect (a predecessor) would help things. It happens to me with spaces between paragraphs.
There was another thread a while back about two spaces versus one space after a period. I believe there wasn't a consensus, but one space is a newer option. I use two spaces. On my Blackberry, when I type two spaces, it creates a period before them. So there must be some fairly large support for the two space option. I would do an internet search, find support for two spaces, and send it to the editor.