During my render the notifications filled up the top-left space on the maniaplanet window (approx. 8 items?). These notifications usually load very slowly since the render causes the game to slow down, too.
After render I get this screen:

Hope that's enough to fix.
Additional Suggestion: Would be great to have notifications turned off during render, since they don't serve a real purpose during render anyway. These things just obstruct the view on the current rendered image.