Unless there is something else anyone can think of...

If the issue is that the terminal is sending SIGTTOU stopping the process when it's trying to write to the terminal from the background (as indicated by ig), you could try  stty -tostop to disable that behavior (most terminals allow it to be controlled):

$ stty tostop
$ echo foo &
[1] 7746

[1]+  Stopped                 echo foo

$ stty -tostop
$ echo foo &
foo
[2] 7748
[2]-  Done                    echo foo
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As you can see, in the first case, the background process is being stopped (via SIGTTOU), while in the latter case, the process is allowed to output "foo" (as if being run in the foreground), and the process can terminate normally.