[CMOTD]

Do you take the photos with a phone or tablet by any chance? This is the usual cause of such errors even though they appear the right way up on your phone.
 
There are lots of articles on the internet which explain the technical reasons for this, and offer various solutions. 
 
But if you want a quick, simple fix, the answer is simply to hold your phone as shown below, with the round home button on the right when you take photos.
 


 
This is the only way that an iPhone will take photos without rotation problems.