TYPO3 Core

- In current TYPO3 Version 6.2.15 this Error only with render mode tree arcurs.
- So mysteriously the second request overwrite the items from first in $config['items'] array and a unknown array_key_exists(0, $config['row']) (screen)

This is my part in a Plugin-flexform:
-------------------------------------
<settings.limits.category>
<TCEforms>
<label>my categories</label>
<config>
<type>select</type>
<itemsProcFunc>Me\FooExt\TCA\SysCategoryList->extendedItemList</itemsProcFunc>
<foreign_table>sys_category</foreign_table>
<minitems>0</minitems>
<maxitems>1</maxitems>
<renderMode>tree</renderMode>
<treeConfig>
<parentField>parent</parentField>
<appearance>
<nonSelectableLevels>0,1</nonSelectableLevels>
<expandAll>1</expandAll>
<showHeader>1</showHeader>
<maxLevels>10</maxLevels>
<width>520</width>
</appearance>
</treeConfig>
</config>
</TCEforms>
</settings.limits.category>