Reverse Invoice bug in 1.2.8-1

[Paul Bente <..hidden..>]

Steps to reproduce:
Install LedgerSMB 1.2.8 and apply Hotfix 1.2.8-1
Create a fresh database and user and import the standard  
US_Manufacturing-chart.sql
Log in
System > Audit Control > Enforce transaction reversal?  NO
Activate Audit trail? NO

Set up a Vendor: Vendor1
Set up a part, part1

Add account 1061 "Cash Clearing" similar to 1060 checking to aid in  
setting up initial inventory. I will purchase the starting inventory  
from the Vendor1 at the correct cost and then "pay" Vendor1 from the  
Cash Clearing account to get the inventory entered at its proper cost.

Add transaction:
Db 1061 Cash Clearing  $1,000.00  (which is the value of the as yet  
un-entered inventory.)
Cr  3590 retained Earnings $1,000.00 (to balance). Ordinarily there  
would be
lots of other asset and liability entries in this transaction  
corresponding to initial set-up. Being able to correct and re-post  
transactions was a real help in getting these initial entries  
correctly labeled and in beginning to understand how lsmb handles  
things.

Now, create an vendor invoice for the parts, 1,000 ea part1 @ 1.00   
totaling our $1,000.00. Post the invoice.  The entries now show up in  
the GL and Report parts shows the correct quantities on hand.  
However, the "Last Cost" field shows no entry. Why? Seems like it now  
should be $1.00.

Now I want to pay the invoice. How to find it? I select AP > Reports  
> AP Aging and there it is. Click the invoice number and up it pops  
with a nice place to enter the payment at the bottom. Enter the  
payment of $1,000.00 and a source note, select acct 1061 and Post.  
Now the warning that I am posting an existing transaction pops up but  
I've seen that before and (I think) I am just revising the  
transaction so OK, hit continue.

Oops. Now the General Ledger shows I have duplicated the invoice and  
I have added another 1,000 of part1 to inventory, paid for out of  
acct #1061 and I still have a remaining CR of $1,000.00 in acct   
#2100 "AP". My first question is how should I have paid the invoice  
as that certainly didn't work?

Realizing that was clearly a mistake, I click on the invoice number  
in the General Ledger, bring up the invoice now showing 2,000 ea of  
part1, $2,000.00 due and one payment of $1,000.00. I attempt to start  
over and remove this invoice by clicking Delete. Am I sure I want to  
delete Invoice P101? Click Continue. The transaction no longer  
appears in the General Ledger, but using List Accounts shows
#1530 Inventory Db $2,000.00
#2100 AP  Cr $1,000.00
#1061 Cash Clearing  shows 0.00
 #3590 Cr $1,000.00 as before

Listing parts shows a quantity of -1,000 (negative!) for part1.

The General Ledger shows only the first set-up transaction and no  
transactions involving #2100 or #1530.

Question #1: What is the recommended way to pay a previously entered  
invoice?

Question #2 Is there a way to clean up or reverse this mess? I've  
done something similar but with a lot more entries. Failing that, is  
there a way to migrate all of my Parts, Customers and Vendors to a  
fresh database without re-typing them to start over?