Incorrect values from every other refresh

Hi,

I have been running power bi for more than a year now and with no problems. Recently I have been having problems with refresh and incorrect values from my measures. 

I have scheduled refresh and it looks like every other refresh I get wrong values. However, they are always the same wrong values. 

For example, sales number in January always go to the same number when the refresh fetches wrong data.

But then the schedule refresh happens again and the correct values appear again. This happens with every refresh. Sometimes less frequently. 

This also happens when I refresh the database in desktop version.

Does anyone know what could be wrong?

Thanks for the assistance

Magnus