problems with audioresample with mulitple channels

[Havard]

Dear list
I am trying to use the audioresample element post to my own element. 
This works fine when "audio/x-raw,channels=(int)2".
But when channels=4, the aduioresample element will complains with 
"FAILED to configure incaps and outcaps.

I am postpending audioresample with "audio/x-raw,rate=(int)1200".
Am I missing some configuration?

Regards Havard