Hello,
Product excerpt is the short description.
You use the divs in the short description and once you limit the product excerpt it cuts of the close div tags and causes the issue. So, if you want to use the product excerpt on the shop page then don’t use divs before symbols limit. For example, don’t use the divs http://prntscr.com/ulvz8u before the 30 symbols of your short description http://prntscr.com/ulvygq
Regards