OK - re-tested 759 on a clean machine here and it works as advertised. So... why are your results different to ours?
We think it may be down to version of sox you have. Please show us the output from sox -h - we want to see the version number of sox.
Also - PWD - you mention internal recording - there is none. You can record inbound, outbound, both, none or OTR. One of the speakers always has to be external.
You also mention OSLEC. OSLEC has not been available since we stopped using our own asterisk rpms (pre ATrpms) and won't be available again until you move to DAHDI (and even then it is a few releases away, although HPEC is available now). What release of asterisk were you running before?
Kind Regards
S