Input cursor jumps to the end of the text after a first letter has been entered (Safari 12.1)

[atomAltera]

Hello. Found strange behavior while going through tutorial.
In chapter "Each block bindings" https://svelte.dev/tutorial/each-block-bindings

After bindings have set. Try to place input cursor in the middle of text in the input box and start input text. After the first letter cursor jumps to the end of the text.

Here is REPL gist:
https://svelte.dev/repl?version=3.0.0&gist=2c4c044cb22819dfa5335e98004c4f27

Here is video demonstration:
https://youtu.be/j1Sdrie3orM

Safari Version 12.1 (14607.1.40.1.4)

No issues in Chrome.