If you are using the TeamStudio Edition 24 CIAO! tool, please be aware of the following bug:
When checking in multiple design elements and ticking the "Use check out comment" option, the check out comments are "erased" and gone is your history.
As a workaround you will have to check in all checked-out design elements seperately !!
This bug has been reported to TeamStudio. However the fix is not expected to be ready until the end of june.