Problem in Trial Balance report with stocks and multiple currencies

[Chang Wang]

Hi all,
I noticed an issue with the Trial Balance report when using stock trading
and multiple currencies. Even when transactions are balanced, the Trial
Balance report appears to break due to incorrect calculation of unrealized
gains.

I've attached an uncompressed minimal example to illustrate the problem.

Steps to reproduce:
Open the attached book.
Generate a Trial Balance report with reporting currency set to USD, price
source set to Last up through report date, and enable Show Foreign
Currencies and Exchange Rates.

Observed behavior:
The report shows an Unrealized Gain of $20,800, which is incorrect.

Expected behavior:
The Unrealized Gain should be $200.

Explanation:
The example contains three transactions:
1) 08/02/2025 - Buy one stock for 10,200 JPY.
2) 08/03/2025 - Exchange 100,000 JPY for 100,000 USD.
3) 08/04/2025 - Buy one stock for 10,400 JPY.

The JPY/USD rate is fixed at 1 on all days, so there should be no realized
or unrealized currency gains. Stock prices are set at 10X00 JPY on
08/0X/2025, where X = 1, 2, 3, 4.

Therefore, in USD reporting currency, the Trial Balance should show
unrealized gains as:
(10,400 * 2) - 10,200 - 10,400 = 200 JPY = 200 USD

Notably, the Balance Sheet report does display the correct unrealized gain.
And if transaction 3) or transaction 2) is removed, the Trial Balance turns
out to be correct.

I'm not familiar with Scheme, so I wasn't able to locate the problem in the
source code. I also wasn't able to file a bug on Bugzilla, since the
registration function appears to be broken.

Thanks for your attention,
Chang
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