Text Editor in Upfront - is impossible

All My sites

Using the Text editor in Chrome ( All extensions disabled)

If i use the cursor, forward and backwards keys to move the edit point within the text and then type the text invariably goes into the wrong place. Is this a universal bug or is something in my setup?

It happens both in a live site and in a theme tester instance.

I have to edit the text elsewhere and paste it complete, which isn't ideal.