Is it a bug or not ? random change in resource while working with Resource Pool Sharing ?? Please help ..

Hi everyone , 

I am experiencing a strange problem with ms project 2016 pro regarding randome changes in tasks' resouces .

The problem appear when re-opening project file again .

I am having two projects files  sharing  one single project resource pool  file locally ..I wonder what could  be the problem  ??? 

Note : I am an advance user of ms project .. 

Thank you ...