Ace broken in code mode?

[LaKing]

I'm getting a bit strange behavior when editing in code view mode. I place the caret and start typing, and the characters appear approx 20 chars before the caret, at a bit random position. When editing a string, the characters can get out of the string, so the json structure is damaged too eventually at a ~random spot. ...

Any ideas what might be causing this?

FF and chrome produce the same behavior for me.
Styling seems not to matter either, ...
jsoneditor 5.9.4
angularjs 1.6.6