[smallstepforman]

.o file stamp newer than .c timestamp. Make figures out file can be skipped. Run recursive touch on these problematic files and headers.

[yxhuvud]

The most fun is when the build then restarts, and do a build cycle until the the clock passes some magical timestamp making the build succeed.

[russfink]

More magical, your object files reside on a network shared drive that has a clock slightly different than that of the compiler machine.