This is really bizarre. I recorded a payment on INV 436. It went fine, except when I went back to the business invoice account to enter payment on another invoice, I noticed that INV 436 was still there and unpaid. I checked the corresponding account where the payment was deposited to, and Quicken did properly record a deposit for INV 436. So I proceeded to display INV 436 form and a message popped out "Some split data lost. Continue?" I tried to delete and void INV 436, but nothing happened, but now I have three INV 436s.
Quicken Classic Business and Personal, R54.16, Build 27.1.54.16. Windows 11.