An edit to a transitioned lease now warns you

The opening balance for a lease you have transitioned is measured at your transition date over the payments still due after it. Change one of those payments and that balance no longer matches the lease. Correcting the rent payment day is the commonest way this happens, and it is a correction worth making: it moves every rent date and re-cuts the part payments at each end.

Lease102 rebuilt the payment and amortisation schedules on the corrected dates, which is right, and left the opening balance alone, which is also right. Re-pricing it from the start of the lease would answer a different question, and the figure may already have gone into your comparatives. What was missing was telling you. The schedule then ran forward from a balance that no longer matched, and where the payments had grown it repaid more than the opening balance supported, so the closing liability finished below zero.

You are now told in three places: the lease form warns you before you save, the save itself confirms whether the opening balance has gone out of date, and the schedule and its CSV, Excel and PDF exports carry the warning until you resolve it. Resolving it is one action: press Recalc on that lease's row on the Transition screen.

Separately, Lease102 now checks that every schedule adds up. Over the life of a lease the opening balance plus interest must equal the payments, so a schedule ending anywhere other than zero is marked and listed in Close Checks.