Disconnect between Balance and Equity (when they should be the same)

 

I'm seeing some very odd behaviour while doing a backtest. There is a large disconnect between my Balance and Equity values. There was a trade to buy 35.1 lots of EURUSD at 1.37321 and the trade later exited at 1.37412, for a profit of 9.1 pips * 35.1 lots * $10/lot/pip = $3194.1 which shows up correctly in the results table and the balance curve on the chart, but then the equity curve shows a gain of about 12,000 instead of what it should be.

See screenshots below. Does anyone know what is happening here?

 
I've seen similar, bug in the graphics. Disappears with more trades.