The possible answer to your problem is on the other end of where your looking. ITs most likely not incubation. I have published and its been discussed on here a million times. That nesting is directly related to hatchrate.
Poor nesting results in poor hatchrate. The general cause is easy to understand. When nesting options are poor, the females hold the eggs longer. In other words, past due. The eggs cannot survive forever inside a female. When the eggs go past due, they become stressed, then die. Normally a female will force nest, that is, nest in inapproiate places, or dump the eggs. As you can imagine, being held past due, places undue stress on eggs(they do have a life you know) Stress causes impact on the immune system. This is not only true for monitors, but their eggs as well. A depressed immune system, means weak eggs, weak eggs equals low hatchrate. Bloodbat, this is very very simple.
My uneducated guess would be. Your eggs have a higher then normal bacteria and other pathogen count. An educated guess would be, have them tested.
Stressed eggs fail at stressful times in incubation. For instance, they cannot take the normal changes in temps/humidity, healthy eggs can. They also fail during "key" changes in development. For instance, after a period of diapause(a change). and just before hatching, when the monitor must convert from being supported by the egg to supporting itself. I know this, because I have experience(bad and good)
Can you imagine what bacteria fills unused lungs work like when asked to start to function.
So yes, its very understandable that you are not progressing, your looking in the wrong place. You have accepted that because your females laid eggs, they did that well. That is in question, as your results indicate otherwise.
To change the subject a little(not really as its directly related). You seem to forget there are levels of all sorts of accomplishments. You seem or at least try to talk like, your very knowledgeable. Yet, you practice being mediocre. As you gain experience with monitors, you move to different levels. This gives you different levels of goals and results. You should no longer have mediocre results. Mediocre defines as, barely adequate. It appears as hatching a baby or two is no longer adequate for you.
In other words, the old results do not work in higher levels of expectations and accomplishments. In a post below, you say your room works, you verify this with your results. Yet, your results are barely adequate(by your standards). So in fact, when your at a higher level of monitor keeping, getting eggs is not unexpected. Hatching eggs is expected. Also reproduction and combined longevity is now a goal, not a few clutches then death with a few hatchlings from many clutches. One baby is great for a beginer, but not great for someone with experience.
You must understand, these results are not about you being anything(good bad mean rude, etc etc) they are indicators of your husbandry. They determine what needs improvement and what doesn't. They are signs, to a keeper, that something is amiss. Consider, its not necessarily about methods, but continued application. Which means, you can have an "ideal" setup, but fail to maintain it properly. This also produces mediocre results. Of course a bad or poor setup commonly(best effort)produces mediorce results, with a slip in maintainence produces very poor results. Or great results are a rarity. The reality is, humans slip all the time. Methods for consistant results must include such slippage.
To the point, the problem with larger monitors is the size and quality of nesting. The monitors are bigger, so it becomes a challange to nest them properly. Your beginer outlook of, she laid eggs in the box means the nesting box is good. Is like I said, beginerlike. Your not a beginer any longer, you should now understand, the percentage of hatch determines the quality of nesting. In fact, the quality of your combined husbandry. Continued poor hatchrate indicates, conditions are poor. Thats all to simple.
Sir, its time you entertain the thought, that something is amiss in your conditions. And begin to attempt improvements. Or do you want to keep seeing dead babies, then showing them to us. I for one, would rather see nice fat healthy babies, then see ones you were surprised made it.
Consider the old saying, its a fool who does the same thing over and over, expecting different results. Then consider, with monitors we are all fools at one time or another. Bloodbat, its time for you to move on and become consistant.
lastly, improving your husbandry is to work on your husbandry, to make an effort of physical improvement. Not to talk to and agree with others on some forum. Sir, that does not improve anything. Its not agreeing or disagreeing, that matters, its results related to your effort that counts. FR
. Do you still have your argus? Also, you used to have a website, what's the address? Haven't seen it since japaleno hatched.