It is hard to find where thing went wrong is balance of the coin never fell negative in calculation. It would be great if wallet balance at certain time, date in koinly could be verified by comparing it to corresponding info in block explorers (on chain). May be some Artificial intelligence(AI) integration could be helpful for that. As well as matching tx from/to different wallets on different chains, matching proper liquidity tx (some time you enter LP and get LP token, than contract is upgraded and when exiting you burn NFT and get your tokens back, and koinly don't understand that that is the same position.) There are many examples like that. Basically if you have many wallets and lot of tx (in DEFI), it is nightmare to get your taxes dome right. Yes, If you have 2 exchanges and 2 wallets, than you can do it in 30min. Also when koinly API get updates for certain chain, you fully resync thinking that those 3 years of NFT tx will finally be imported, all you get is dublicated tx, and now have to spend even more time. You need smarter engine, with AI something else. All date is on chain, you just have to grab it, read, and import accordingly.