Scaling up means a lot investment but what happens when the demand goes down? You're left with debt from it and little demand. The scaling as such is not the problem here.
Of course keeping a few machines in the wings is probably cheaper than overtime and unemployment.
[edit] I'd also like to know how difficult it would be to just switch the machine over to making cheaper, non-medical grade masks as demand changes?
I suppose it's more realistic with cnc or 3d printing but even then it's not that simple mission, this small company wouldn't most likely try or want to be "aws but for x robots" : )
I suppose if you think about 3d printers, plastic molding, cnc, then we are slowly going to this direction.
I'd be willing to bet that you are right though and that the machines currently being used wouldn't be capable of producing much besides masks.