I sort of use the following to figure out what went wrong with a given egg:
-molded early most obviously a non fertile or DOA egg
-dried up early as above or too dry a substrate
-molded mid incompatible with life embryo, contamination or incubation problem (usually too cold)
-molded end often still viable but also can denote embryo death. These can be many things, egg got too dry over time, temps incorrect, genetic problems, weak embryo couldnt get itself out, no egg tooth formed, egg suffocated. O2 requirements increase as the embryo gets larger, lower surface area to volume ratio=less O2 available for the growing tissue.
-dried up late likely forgot to add moisture over the incubation period.