Why does the editor randomly change a section's background color?

When using the editor for a campaign, from time to time it changes the background color of a section for now reason.   This will happen about once every 10 to 25 edits of a campaign.   It's risky in that you can't count on the last version before you Schedule it to be emailed to not have a background that is miscolored, so you have to carefully check (and sometimes repair) the campaign before emailing.