When in the blueprint sandbox (https://mods.factorio.com/mod/blueprint-sandboxes), if I place a pump and then press the shortcut to change the configuration of the pump to whatever is next after default, the pump item disappears/is deleted. It seems that the Blueprint Sandbox is not able to show pump in it's alternative states. Is that a Sandbox thing or a issue with the Configurable pump?

I'm assuming you're playing with Nullius based on this discussion. In that case the fault is in their mod code, you're interacting with one of the Nullius pumps, which has extra scripting on top of the functionality my mod provides. My valves function perfectly fine in Blueprint Standboxes, I just verified. Please raise the issue in the Nullius mod.