Always hatch upside down?

Ive been having some troubles with my new incubator i got for this year. First of all i cant seem to hatch anything. I dont know what im doing wrong but for example i set 36 different eggs and its now hatch week and im left with about 7. Its been like this all year and ive hardly hatched anything! Fertility has been high and the temp has been kept between 37.4 and 38.4C and humidity at 40% till hatch then up to about 60%. The incubator is a hovabator for 42 eggs with an automatic turner.

Secondly every egg that makes it to hatch date ends up pipping upside down? the air sacs are big enough but they pip at the small end all the same! I normally stop turning 4-5 days before hatch date so whats going on?

Yeh im pretty sure they're accurate, how would you find out if they weren't? I had problems with a dodgy thermometer earlier this year and im now using a different hopefully more accurate one! Im using the same hygrometer that i used in my old incubator which hatched the eggs fine. If it makes any difference the only hatch ive had a good rate with in this bator was my quail. I only set 7 eggs and 6 hatched fine! Its not always 4-5 days before hatch date that i stop turning, i usually go by candling, when the embryo fills up the whole egg and doesnt have any more room, thats when i stop turning. Its just usually 4-5 days. I will try turning them for longer on my next hatch! Yes when i put them in lockdown i just take them out the turner, remove it and lay them on the floor
 

Ridgerunner, Mine is a still air and i didnt realise i should be measuring the temperatur from the top of the eggs! Maybe the bator is getting too hot then, since i measure the temperature from about the middle of the egg. When i store them and right the way through incubation till lockdown i sit them with the pointy end downwards. Thank you i'll have a read through your link!
 

Thank you, ill try calibrating them before i set more eggs. Right now i have a few eggs hatching. I had 2 turkeys pipping but one never made an external pip and died and the second was almost out but must not have been ready cause it bled to death during the night! Im now left with 2 ducks eggs hatching at the small end that cant seem to get out. They made a small pip hole 2 days ago and yesterday i decided to start trying to help them cause they hadnt made any progress. Ive been slowly peeling back the shell and membrane from around their pip hole and i havnt gotten very far since there is still small veins on one of them. Should i keep peeling back to get them out or what should i do now? They dont seem to be making any effort themselves even though they are cheeping enough!