Current P&L in SGD Total is not Current P&L of SGD + USD converted to SGD directly.
Current P&L in SGD Total = Current Value in SGD - Current Cost in SGD
Usually, such cases is caused by a wrong FX entry in the transactions. In your case, I see that is likely due to your Apple Inc transaction → Edit Transaction
Yes, this is caused by the wrong transaction stated above.
Tips: You can check out this page → Transactions list - StocksCafe
It will have red * on the price for weird FX input. Also, there will be highlights in red for potentially incorrect inputs.
Same. This is caused by incorrect inputs
You have entered a GBX 17.1 as the buy price per share while the current price for this stock is GBX 1380.