Hello @NorbertD
Thank you for reaching out on the community and telling us about your issue. I do apologize for the issue you're having. I'm wondering here how you might have added the payment? Did you go to the loan register and add it as a transaction or did you do it in a different way? We should be able to add an extra transaction without it adjusting the rest of the transactions ideally. Another thing is you could just add it for today rather than prior and it shouldn't adjust any of the previous transactions either.
Either way please let us know if this helps you out. If not we'll see what we can try next.
Thanks,
Quicken Francisco