The moving average is not calculated wrong.
you only have to understand that the 262 movement valuation is just quantity * moving average.
and the 161 is a proportion of the PO price, which has probably more than 1 condition or a different price unit.
you can re-calculate any number of your report and should come to the same result as the report and as I did, it is mathematically correct.
your PO price is 10.94181818181818 per 1
the first moving average in the report is 10.95
for the same quantity of 11 you get 2 different results
based in the moving average you get 120,40
based on the PO price you get 120.36
This will usually not create a big problem if you work with higher quantities or when the stock becomes zero.
but in your case it is creating a big problem since your goods issue with 261 movement is long ago, not even listed in the report, and you are doing a lot reversals with 262 and subsequent returns which always left 2 as remaining stock. And this small stock gets always the rounding differences and hence becomes more and more expensive.