Also, possibly a misfire. The clamp is under spring tension that can approach 50,000 Newtons, and the separation mechanism can use explosive bolts.
Not sure which configuration this launch entails but the telescope itself weighs 6,500 kg, so that sounds like a lot of energy to account for.
Ariane 5 user's manual, PDF: https://www.arianespace.com/wp-content/uploads/2015/09/Arian...