Questions about operation of pneumatic valves

[FrankJ]

We always use single solenoids unless we need the bi state feature. But yes, as you found out, bouncing a dual solenoid valve just right can cause it to shift. As others suggested, leaving the solenoid energized will stop that behavior. I have solenoids in the plant the stay energized for years without damage.

[GeeTwo]

Most solenoid valves, including the VexPro ones you are using, have a small button to manually switch the state. Is it possible that in the banging around some part pushed that button?

[Abrakadabra]

Thanks for all the replies! This is an issue that has just recently appeared, so it could very well be a wiring issue, but now that we know it's safe to keep the solenoids powered, we'll try that as a first approach. And knowing that mechanical shock can indeed be an issue, we will try the shock mounting remedy as well.