You have a text field in that if you constant type the line will not break, but using the RUI UI the line will brake.
In Cloud for Customer HTML5 UI.
Reproducing the Issue
In any text field do a constant type.
It's a default behavior/limitation in IE or Chrome browser. RUI uses different Third Party Library for RichText. HTML5 uses TinyMCE library which has this limitation.
Also in IE you will see a horizontal scrollbar and in Chrome it will only appear after you click out of the text field.
Text Field, Break Line, Scrollbar
KBA , AP-RC-UIF , C4C UI Framework , Problem