Steps to reproduce:
Create an element. Apply a transition on hover. Apply a named easing “eg. In Out”. Change to a custom easing by dragging the handles on the cubic bezier interactive chart. Then type directly in the text panel where the cubic bezier code is generated from the interactive chart. Delete lines of that code and press enter. Site crashes or attempts to reset the easing to a named easing fail.
Temporary Fix:
Set the cubic bezier generated text to read only