TYPO3 Core

we recently updated our Typo3 4.6.4 instance to 4.7.1 without any big problems, only to realize soon that the PageTree-filter is not working for Admins.
If an Admin enters a UID or phrase into the filter no page gets found and all existing pages except the typo3-root page and another page on root-level are hidden in the PageTree.
As an Editor the PageTree-filter works just fine.

Downgrading typo3_src to 4.7.0 PageTree-filter works for both - Admin and Editor. Upgrading to 4.7.4 doesn't do anything for this issue.
I managed to determine the crucial code-snippet that is causing this behaviour:

l.228-240 in t3lib/tree/pagetree/class.t3lib_tree_pagetree_dataprovider.php of Patch Set1 (https://review.typo3.org/#/c/10376/):

if ($mountPoints != array(0)) {
                $isInsideMountPoints = FALSE;
                foreach ($rootline as $rootlineElement) {
                    if (in_array(intval($rootlineElement['uid']), $mountPoints, TRUE)) {
                        $isInsideMountPoints = TRUE;
                        break;
                    }
                }

                if (!$isInsideMountPoints) {
                    continue;
                }
            }

If I remove this block from the code, the PageTree-Filter works just fine - for any user. On integrating it, PageTree-filter breaks for Admins.

I did not perform any altering of the mounting-configuration for the Admins on or after upgrading from 4.6.4 to 4.7.1, so maybe it is due to some old setting that these accounts are causing trouble with this mountpoint-routine?