I have been through that mental loop and the altitude error is so large that it would require a mis-read on the scale of the 'old' 3-pointer altimeters (the '10,000ft error' to put them in the sea there. I think the entry altitude should be 6000ft = around 200mb?
One other possibility is some sort of 'home-built' let-down to a 'round-the-rock' visual - that went wrong - then you could look at a sub-scale error?