Datastream - Latest Value only

I've created a streaming dataset in my Power BI Web environment. I need to show the live-data in a Dashboard.

Therefore I connected to the dataset in Power BI Desktop and I'm getting the data as expected:

The problem occurs, when I want to show the latest value (percentage) only:
Sometimes it does show me the latest value, but it quite often doesn't return a value at all (-> blank).

Similiar issues when I try to show N Top values only in a table: It doesn't return the requestet amount (e.g. I chose N=10, but getting back two values. After the next data push, I've got just 5 values listed....

I've tried to create a measure as well, but same problem:

Most Recent Max Rate = 
VAR LatestTimestamp =
    MAX(RealTimeData[timestamp])
VAR LatestMaxRate =
    CALCULATE(
        MAX(RealTimeData[percent]),
        RealTimeData[timestamp]=LatestTimestamp
    )
RETURN
    LatestMaxRate

I suggest there might be a date formatting issue, but I've no idea how to solve it.

Does anyone have an idea what I'm doing wrong here?