TYPO3 Core

After translationg my Main-Page, which is also my Mountpoint for users, i got a strange error.
Everytime a user tries to edit the page, he got an error.

Attempt to modify record '%s' (%s) without permission. Or non-existing page.

The problem occours only on the mountpoint and for all languages. Even when editing the main language. I guess because of the intecreation of the table pages_lanugages_overlay.

My workaround:

typo3/sysext/core/Classes/Authentication/BackendUserAuthentication.php

in the function isInWebMount (Line 389)

I changed this
// Check if input id is an offline version page in which case we will map id to the online version:
$checkRec = BackendUtility::getRecord('pages', $id, 'pid,t3ver_oid');
if ($checkRec['pid'] == -1) {
$id = (int)$checkRec['t3ver_oid'];
}

to that
// Check if input id is an offline version page in which case we will map id to the online version:
$checkRec = BackendUtility::getRecord('pages', $id, 'pid,t3ver_oid,l10n_parent');
if ($checkRec['pid'] == -1) {
$id = (int)$checkRec['t3ver_oid'];
}
elseif ($checkRec['l10n_parent'] > 0) {
$id = (int)$checkRec['l10n_parent'];
}

And solved my problem. I guess it is a problem with typo3 and not of my configuration, but feel free to test it.