SMART OBJECTS often don't save and update properly to the master document.

I've had this problem a while, across various versions of photoshop including the latest. MAC OS.

Assume I have smart object inside a master document. When I double click the smart object to go inside and edit it. Often, when saving; it appears the smart object saved correctly. HOWEVER; if I close the smart object window, go back to the Master document and open the smart object again. The changes that were saved, were infact not saved.

This bug has cost me countless hours of work, but I cannot work out why sometimes the Smart Object will save and update, and sometimes not. The only way of knowing is closing the master document and opening it again. 

Another note to add; If after editing and saving the smart object. I do not close it, when going back to the master document and and opening the smart object again, it will take me into the smart object window. Giving me the illusion that the smart object I'm working on is in fact updated and saved. When it actually isn't.