Yes, this does affect optimisation. Although I have not personally contacted the service desk about this issue, I do believe that MetaQuotes are aware of it (see link below). However, since this only occurs when using externally generated data, they don't seem to be too worried about fixing it.
1. Launch MT4 as usual via the Tickstory launcher (probably also works if launched directly).2. In the MT4 Strategy Tester, select your desired spread.3. Select the “Control points” modelling type and press the ‘Test’ button. You can immediately stop the back-test once it has started. The selected spread will now take effect.4. Select the “Tick” modelling method and continue back-testing as normal.5. Repeat steps 2-4 whenever you wish to change the spread.
I don't know what you mean by "act, wait, act, wait" but irrespective of what application you use to download the tick data or to produce the ".fxt" and/or ".hst", the spread problem is the same.
The only exception is if you use Birt's "TickDataSuite" to launch MetaTrader, which corrects the problem, but if you launch MetaTrader independently, the problem persists for builds 920-950.
That is why I use build 910 to backtest, until a more permanent solution is available!