BeSafe Stretch is getting lots of (unwanted) attention due to a defective harness. A thread on the largest Swedish Facebook forum for carseats with 56k members have 230 comments where lots of parents share photos of a defective harness. Somehow the harness is damaging the plastic.
If you are using BeSafe Stretch then immediately check your harness for damages to make sure the seat is safe to use. This issue is very new and BeSafe are apparently asking parents to send in their seat for harness replacement. More updates will follow.