Haven`t find any kind of such problem at the forum.
I`m always ready to move my funds out from the Dukas, because it is already at least 5th time I encourage non-market execution during about one month of trading here. I wrote to support at the first time I encourage the problem and received the answer like everything is going like it should be. They don`t think that it is a problem.
Now, after about one month of trading, I decided to write about it on the forum to verify if this problem occurs to all or only to me.
I haven't find any negative feedbacks about Dukas over the internet so I believed that such kind of problems are likely to be met at low level brokers but not Dukas.
I was sure that it is a bug or technical problem, but support answer another way.

I had a 0.1mil short order on EUR/USD. Today I decided to close this order during American session manually. The market was flat.
Here is the Screen of what I received (M1 timeframe):


As we can see, such a small order (only 0.1mil) was closed by two parts. One at about 1.3352 as it should be, and another part at about 1.33625!!!

Here is the tick screen:


And this is not all)))
Here is the activity log screen:

As we can see, the order was filled at 1.33525 price.

The same confirmation we can get from the trade log:

It is like all the order was filled at 1.33525 price.

But actually I was billed at 1.335583 as we can see from position report:



It is the first time I have such a problem with manual closing of the position ever.
But I have regular problem with stop loss execution.
Fist, SL is sliding constantly up to 20 pips.
Second, I had several times non-market execution of Stop Loss like this:


This SL was moved to Break Even at 1.32235 but Dukas closed it -21.5pips

Everybody has such a problems here?
Is it usual for Dukas?

The problem is in the different amounts used in your example to describe the situation. You show 100K of the close amount in the Activity log, whereas there are 150K shown as the closing amount in the Position report at the average price of 1.335583.

The details of the trade are below:
The position 23537491 was open on the 12.09.2013 at GMT 12:30:09 in the amount of 150K. It was closed twice. First 50K were closed at 1.33625 using the Iphone/Ipad app at GMT 12:55:10 17.09.2013. The other 100K were closed at 1.33525 GMT 15:27:08 the same day. Hence the average close price 1.335583 in the closed positions report.

Obviously the JForex chart shown above was left open when both the first and the second close orders were submitted. The bug in the chart showing the close points of the positions possibly made you think that both closes were done at the 15:27 minute, which is not correct. The refresh of the chart displays the closes correctly:


This bug with the position close points display on the charts will be investigated and rectified.

Unfortunately the other statement of yours: "But I have regular problem with stop loss execution." is not specific, so we cannot reply with an explanation. However, taking into account that some of your positions, including the one above 23537491, were executed in the news time, we believe that the orders were executed according to the market conditions at that moment.