Page lags ocurred when large text entered

[LentCrown]

If entered text too large, page starts to lag (only piece of page displayed). You can scroll page down, but piece of page from which you moved, will disappear and if you will scroll back, you must wait for it to display again. Problem occur in both 'laic' and 'nerd' modes.

Picture 1 (Normal page work):

Picture 2 (Entered large text, only part of text displayed)

Picture 3 (Same large text as on picture 2, but I scrolled down)