erronous spike in squarewavesignal using rp.h

[Chris78]

Hi,
I am a newbie in programming the redpitaya and have problem using the sample "continuous_signal_generation.c "
I want to generate a squarewave-signal by changing the sample codeline

"rp_GenWaveform(RP_CH_1, RP_WAVEFORM_SINE);"
into
"rp_GenWaveform(RP_CH_1, RP_WAVEFORM_SQUARE);"

The problem is a spike in the middle of each generated squarewave pulse.
To verify the hardware I tested the "Signal Generator Utility" and it works.
But I need to generate some special puls-signals and therefore the use of "rp.h" is mandatory.

Are there any ideas to cure this "bug"??

Thank you in advance.