My hatch method were very old school. Some will hatch out 6-7 days later. Someone told me they already using the aim temperature to every sign eggs by using small led to the eggs. Just like hatch a bird or chicken. Maybe you can try that out to reduce your hatch time.
What do you mean by "problem"? What is your concern?
I have extremely accurate and stable temperature and humidity in my incubators for TSD studies. Proportional thermostats and higher end, redundant thermometers/hygrometers. For my sulcata eggs, they always hatch at 82-88 days. This year's were done at 89.5° and 85%-90% humidity. 84 days to hatch with no scute abnormalities at all.
You have something different going on with a 75 day hatch, I would check your thermomters' accuracy and/or daily spikes in temperatures. Do you monitor temps with sensors and reading every 5 or 15 minutes to see what is actually happening during the course of a day. You will be surprised over simply looking at a high/low a few times a day. Do you get any extra/abnormal scute hatchlings?