Very little risk of arcing under normal conditions, but batter them around a bit (possibly bending the leads on the neon bulb if it's not stuck down, don't know if the voids are that big) or subject them to overload conditions, and sure, it's possible. If they are UL listed, it's pretty unlikely normal use or wear conditions are going to cause issues, but perhaps this is something to contact the manufacturer about to confirm. If you have a hipot tester, you could pick a heinous looking example and see what it takes to make it arc if that gives you some extra confidence. If the parts are stuck down and the gaps between things are several millimeters, I think it's unlikely the mass is there to allow leads to bend closer to start arcing issues with large impacts.
A probably not cheap option would also just be to inspect them before you send them out. If in low enough volume or short enough run, it may be cheaper to buy extras and reject some if the supplier's QC isn't up to your standards, but I'll admit this is a bandage rather than a cure.