Well not everything that gets detected is guaranteed to work perfectly.
I guess md5 and sha1 need a lot of computing power on big files and put the processor under heavy stress. This causes considerable heat, in the summer particularly. Overheating is known to cause calculating errors sometimes. How's your computer's ventilation and cooling system doing?
Intel has some Linux information
also. Take a look at this
for example. Some BIOS tuning might help. Then again, it might not.