I have recently seen several "project pinballs" in my workshop that have been safety hazards. I keep a log of all games that are sent to me for repairs, but recently I received a game that "exploded" once the customer brought the game home and plugged it in. I've been repairing pinballs for many years, and technically, I have a process I undertake prior to even plugging a game into the wall socket - regardless of where it came from (country of original) or where it was bought from (private or dealer).

I think all project machines are safety hazards, or at the very least should be treated as that.
There have been a lot of these machines for sale on ebay recently and they have been fetching good prices, a bonus for sellers who don't want to over commit on a lesser valued title.
We are in the age of the handyman and everyone thinks they can fix anything.

There is also the issue where machines appear to be missing a relatively small part but this turns out to be a part that is extremely rare and in some cases the machine won't work without it.