The release is working now.
I’ve deleted my custom Ichimoku-indicators (cs.file). They caused the trouble.
If someone is interested how to do this:
Go to the folder documents\NinjaTrader 8\bin\Custom\Indicator\ - delete the indicator(s)
Open NT, go to the NinjaScript Editor, choose any indicator and compile (button in the head or F5)
Restart NT. Then I’ve installed the new release and it is working now.