[TYPO3-mvc] TYPO3 renders blank page *sometimes*

[Marcus Budzyn]

Extbase, TYPO3 V6.2

In my action I assign the result of a custom query:

$this->view->assign('$games', $repository->findGamesXYZ());

In my fluid template there is a for-each which traverses through the game-array and displays various attributes. The for-each contains several conditions and partials, quite complex but notthing extraordinary.

Problem:
This all works *fine* whenever it is called for the first time. 
If it is called a second or third time a *blank page* is rendered. 

What I tried:
I tried to remove some code from the for-each, but there isn't a specific part to be blamed for this behaviour.
If i remove the entire for-each block, then the page is rendered just fine *every time*.

The amount of data being processed here is very low, the custom query delivers less than 10 objects.

is there a good way to trace this problem? Are the certains logs that could offers some insight?

Final remark: I have other custom queries in that extension that work just fine.

Any (any!) suggestions are welcome!