Average calculations in Power BI get wrong

I have an issue with the calculation of averages both within a table and a clustered column chart - the calculations are wrong and I don't have the slightest idea how to combat it. 
I have several levels in the table - same as in the chart. On the pic you see part of the numbers, the ones with an icon on the right are the bottom level, the bold ones within the red frame are supposed to show the average, so when I calculate the first 4 numbers I get an average of 2.975, not 3.1, for the bottom 4 numbers my average is also 2.975, not 2.8. Same with the green level, with my numbers it should also be 2.975. 
And my overall average is 3.0 whereas my table and column chart show 2.7. Is that a bug?