Since the introduction of the queue in Route Manager and History Viewer, there have been several down-times where the queue became very very long without anything being processed. The reason why nothing was processed was that someone tried to use the “Relation Blame” on very big relations, such as http://www.openstreetmap.org/browse/relation/107796. I have therefore disabled the Relation Blame function for now.
The reason why the queue got so long (sometimes several thousand requests) is probably caused by bots. Probably beacuse of the links that the Wiki automatically creates to the two tools. I suppose I will have to add a robots.txt, and if that does not help, a Captcha.