I'm going to throw out a complete guess of yes.... I would think the heat combined with stagnant water in unused panels would not only get really nasty...but the sitting water couldn't possible be good for the material the panels are made of.
If you leave water in the panels, it can heat up to the point that some panels can soften. The weight of the water in the pipes pulls a vacuum on the panels. So the panels can deform and be pulled closed. Best to drain them when they shut down.