TYPO3 Core

I am using Firefox 43.0.4 on Ubuntu,
pasted a simple comment: ## POSTGRES

sometimes it works and sometime not :/

I tested it with Firefox 45.0a2 and can't confirm the issue :(

Same result but other cause by Firefox 43.0.4 on Windows: (in Chrome not reproducable, too)

TypeError: next is undefined
UndoHistory.prototype.shadowChain() undo.js:342
UndoHistory.prototype.updateTo() undo.js:181
UndoHistory.prototype.commit() undo.js:164
Editor.prototype.replaceSelection() editor.js:692
Editor.prototype.reroutePasteEvent()

A second try delivers the same cause as above mentioned:
TypeError: pos is null
removeRange() undo.js:367
UndoHistory.prototype.applyChain() undo.js:375
UndoHistory.prototype.updateTo() undo.js:182
UndoHistory.prototype.pushChains() undo.js:117
UndoHistory.prototype.push() undo.js:111
Editor.prototype.replaceRange() editor.js:780
Editor.prototype.replaceSelection() editor.js:698
Editor.prototype.reroutePasteEvent() editor.js:768

Tested in TYPO3 7.6.2 and Firefox 43.0.4 stable -- seems to work as expected.

Tested TYPO3 7.6.2 with Firefox 44.0.2 stable on Windows 8.1 and
can confirm a similar problem: only the first line get's inserted.
The cause: NotFoundError: Node was not found undo.js:383.

The problem still occurs with 8.3-dev and Firefox 48