Referring slippage I just saw the actual last point on the bug list:
> Slippage simulation was not 100% neutral in some cases, but affected by the price slope inside the current bar (fixed in V 1.52.0).
But the 1.52.0 ist not yet available, it's the 1.51.9 as beta on download page.
I've just tried it - the problem is not fixed in the beta version.