Easily found a discussion from 2019 that was closed.
I just want to point out that the error is still occurring, although not consistently.
I finished converting 4 Vanguard admiral funds to ETFs. Two completed flawlessly down to the penny. The final two had the same error as in 2019 - Each of the dividend reinvestments (around $100/quarter) were assigned a cost equal to the total cost basis of the entire fund. I had to manually go in and replace the total cost for each transactions on those 2 conversions.