Four tray model D Hatcher very big very old. Holds 500 large eggs, Has fuse box on the side. OK , I've never had this problem before with the sportsmans that I had. The bottom tray hatches great ,the next tray hatches fine, the next tray hatches so so and the top tray barely hatches at all. It's driving me crazy 125 eggs to the tray. I put the eggs I want to hatch for myself in the top tray and 18 hatched , the bottom tray hatched 89. Whats going on? I'll be back in a few ,got to go shut the chicken house doors.