Netcat: Illegal instruction Or Trace/breakpoint trap

Hello Forum,

I want to send some udp packets with netcat. I have installed the small netcat 0.7.1-1, not the bigger ncat packet. I open two shells. On the first I create the server:
nc -u -l -p 23990
And on the second I create the client:
nc -u 127.0.0.1 23990

After sending some chars, I get error messages.
On LEDE 17.01.4:
Trace/breakpoint trap
On LEDE 18.06.0:
Illegal instruction

If I install the bigger ncat packet instead, I can send udp packets.
Its only for testing firewall rules, I can use the bigger ncat and deinstall it later on, I dont need a fix.

Thanks

Peter

busybox netcat doesn't support udp IIRC