Update :
I don't think there is a problem with the mutate function but with the IDE since the log files says : "ERROR system error 10053"
which looks related to this post : RStudio crashing when navigating through file explorer (system error 10053)
I thought it was related to the versions of my sessions , so I updated everything but the crash is still there.
I can provide a .mp4 video that shows the crash via pm if someone is interested since i can't post it there (format not accepted).
I can't think of any solution