It is a Webspinner that is summoned, you can tell from the 16 mana cost. Giant spider is only 13(?)
This has been happening for years, literally since the day Vash was released. There’s many threads about it already and devs have investigated but have difficulty reproducing it for some reason
Edit: here’s when I first reported it. There are other threads too [Reported/Investigating] Vash + A. Weaver summon freezes game?