Ok, this is now 5 months old, and it's down to 958g. I cut it open, and it is full of holes like a swiss cheese! Also, had a blue contamination inside, though contained enough that it could be cut out. It doesn't smell foul, and I've had a wee nibble. Tastes like a swiss. A touch bitter on the finish, but so far, no ill effects. I did make a Beaufort a few weeks before this one, but in between I had made a Lancashire and a Feta and neither of them showed any contamination from the PS I used in the Beaufort. I've never had a wild PS contaminate any of my cheeses before, so either a weird coincidence, or somehow I got some PS into this cheese and it really took off. The odd thing is that the strain I have is not supposed to produce a lot of gass, leading back to the wild PS theory.
Still not sure if this should be eaten or binned.
P.S. I've had another nibble, and while there are no ill effects, the bitterness that was noticable right out of the cave seemed more pronounced (to me, but Vanessa didn't even notice it before, so ?). It doesn't taste anything like gouda. I'm thinking this goes in the bin. The taste, once warmed up, is not great, there is clearly some sort of contamination (yeast, or a wild PS), so unless Vanessa likes it, I'm not sure this is worth keeping. Oh well, only the 2nd cheese to get binned, so not a bad run.
P.P.S. Ok, it seems I'm being overly particular. Vanessa thinks it's fine. So, we'll eat it. Not one I would want to replicate, but edible.