I stumbled across this behaviour after I refunded a payment and made the payment again. The app usually groups a payment and a refund and displays the payment as refunded. In my case the app also grouped the third entry (the second payment) making the entry negative again.
This is behaviour makes sense.
When I tried to move that entry to a different account it only moved the refund but still displayed the entry as being a payment with a negative sign.
This results in accounts looking like this:
Support claims that fixing/changing this would be a feature request. I think this is a bug in the app.