There will always be errors as a result of sampling error but...

There will always be errors as a result of sampling error but this error may often work in favour of the miner remember.

No expert granted, but i could perceive more 'losses' when the dore was full of impurities, but that's inevitably after the gold has been removed.....

I think where you're coming from (initial question) is whether there may be a material (significant) loss of gold - to the mine's account - from the gold in the dore to the gold or money equivalent received from the refinery post refining of that dore?

It's a clear no. Short of some fraud!