I understand, that in this situation you’re giving the loan to somebody - yes?
Can you show the loan’s opening transaction? It’s important, that the opening transaction has the same price as the Initial price configured in the Interest → Advanced tab (which is just 1 by default) and quantity to be the amount you’ve lended.
So you lend 50k units, for the price of 1 each - and the price gonna grow with the interest. I think you’ve lent 1 unit for the price of 50k which immediately lost value to 1.19 - hence the negative return.
The interest payments will show as transactions. The due date is 18 months away from the day you opened the loan with Buy transaction. You can choose a hold date period from the date picker, to see the whole duration of the loan - from start to finish.