Update for anyone interested:
I added a line in /etc/asound.conf to reduce the sample rate to 16000hz:
pcm.array {
type dsnoop
slave {
pcm “hw:wm8960soundcard”
channels 2
rate 16000
}
ipc_key 666666
}
No more error messages for now at least. Only two out of the six buttons work, and I still have to find a way how to get my first sample played but will see how that works out.