Richtext CKEditor slow typing with large content

[lelikflegma]

Hello.
I have issue with Richtext area (CKEditor v4.3). When content is too large (for example: "Reply" case with content of few previous articles), typing message becomes very slow and browser freezes. In previous version of CKEditor 3.6.6.1 it works fine. You can reproduce this bug even on OTRS Demo page:
http://otrs-demo.otrs.com/otrs/index.pl ... rd=otrs123
Open any ticket, try create Note and simple paste any big html content into Richtext area. Then try type something.

I use OTRS v 3.0 with upgraded CKEditor from v 3.6.6.1 to v 4.3