Error: webpack-dev-server: command not found

Hi. I’ve started running into the following error on my project, sprout-mambo:

/opt/watcher/app-types/node/ line 51: webpack-dev-server: command not found

This seems to be stopping me from viewing the project or rewinding it. If I try to remix it, I don’t get the error, but the stylesheet and other aspects of the project no longer load.

The project was private, but have made it public just in case someone can see what the issue is.

(I’m not really much of a coder, so any help would be greatly appreciated!)