I do not think this is the case. I would appear that Propshop was owned or partners with a German firm, Voxeljet, a 3d printing machine manufacturing company http://www.voxeljet.de/en/. The Propshop web site is registered to Voxeljet UK Ltd.I think Prop Shop bought several very expensive 3-D printing machines, and thought they were the answer to make quick props and then thought hey let's make prop replicas to sell to the public. Since they really did not know anything about the 3-D printing process, when all hell broke loose, they did not know how to handle the mess they had caused.
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So someone knew a great deal about 3d printing.
EDIT: Here is an article I couldn't find earlier about Voxeljet acquiring Propshop: https://3dprint.com/17503/voxeljet-acquires-propshop/
Trust me when I say, there are a hundred reasons a company can fold and few of them are ever expressed here. Having owned a Motion picture prop & Effects company for 31 years, and been screwed on a partnership creating prop replicas, the reason things fail is usually a very complex series of events starting from a simple issue. The simple issue is not why a firm goes under, but it often is the catalyst.
I picture a scenario something less sinister and more human:
A minor product issue, disagreement or indecision by managements on how to fix problem, additional projects and their issues adding pressure to completion schedules, driven by a lack time or of cash flow, caused by poor cash management or unexpected overhead costs. In the end, twenty small issues line up and the whole thing starts to fall apart. Then at some point you realize either you can't recover, or it will be too costly to recover (Both in $$ and mental energy), so you say close the doors.
But, I have no idea what the real reason was and all of this guessing is quite useless.