Campaign Merge Fields Used In Preview Text Not Copied Properly

I use campaign merge fields in the preview text of my emails.
I just discovered that when I copy a campaign all the merge fields are newly generated from the old campaign and new merge field placeholders are assigned to the emails and subject line etc. The only place the campaign merge fields are not properly generated when copying the campaign is the Preview Text field. Hope this can be solved. Now I manually have to edit this field in every email every time I copy the campaign.