I'm not getting data with samprate=768k

I'm trying to run WebSDR the same way as in Maasbree Netherlands using the rx 888. My Radiod instance is working fine with samprate =768k in the .conf file. But it doesn't send the data to the multicast. And because websdr is configured to receive the raw iq stream via fifo, it does not start. In the file Radiod@rx888.conf looks something like this

[WEBSDR_768] 
disable = no 
data = websdr768-pcm.local 
mode = iq 
freq = "3700k 5300k 7125k 14150k 21200k 28350k 28850k 29350k" 
samprate = 768k 
low = -383k
high = 383k 
agc = 0 - We do now want to enable AGC if we wish to have a calibrated S-meter.
gain = 20 - Th

What could be causing this?

I suspect that pcmcat does not work with streams greater than 192 kHz.