Wow, it's nice! I thought you had a commercial bator for some reason. I'd really like to have one like that!!
If it's a new problem, is it possible you have a bacteria or mold or anything in there? I see that on the list that Brindle posted as a reason for late loss of embryos, too. I just bleached mine before I put the SF's in, but I always worry about that, especially since those SF eggs are pretty dirty and there is so much dampness in there all the time. I know that I've read that once you get certain strains in there that they can be hard to eradicate even with thorough cleaning. And they can carry from hatch to hatch, even with what seems like thorough cleaning to us. Especially on porous materials like wood. (Not sure what's on the inside of your bator. May not be wood. But I see the cabinet and so I mentioned it.) I know from nursing school that even a few mold spores left behind can multiply. They are invisible to our eyes, but breed really well on porous surfaces.
If it's not that, I can't imagine what besides temp and humidity it could be. But if that wasn't a problem before and you haven't changed anything with the bator, then that just doesn't make sense to me.