Thanks. I indeed did some FX trades (IdealPro) as well as currency conversion (FXCONV) in USDJPY, which maybe why it was messed up. First time happened to me. I manually cleared the erroneous position.
If the base currency of your account is in USD, whenever you trade in a currency that's not based in USD like USD/JPY or USD/CAD, you need to convert the proceeds back to USD after you close the position. IB, unlike some brokers like Oanda, does not do that currency conversion automatically for you, it's you who have to do it and of course incur another commission charge for it otherwise you will always have a position open and incur carrying charges and further profit/loss on it due to the currency fluctuation. If you did a currency conversion, make sure you use "FXCONV" instead of "IDEALPRO" as the destination when you send the order otherwise after you converted the currency, you will end up with a virtual position because IB thinks it's a currency trade and not a conversion and thinks you have a position open when you don't.
That only makes sense when the accumulated foreign currency pnl is large enough. Otherwise I just let it sit there for a while. Small amounts don't cause damage, especially not long positions, though one wants to be careful about negatively yielding currencies in this case.
So you also bet on the weakest horses in horse races? Or the lowest qualified cyclists in the tour de France? Makes zero sense...