Did you also try:
run >NIL: <NIL: mclk
This could help detach it from the CLI.
Another option to try, move it to your s:startup-sequence from startupII in case the problem is that it is started from a shell instead of the initial CLI.
The reason StartupII exists is not because it is a "user-startup" style thing, but so that resident and other shell-seg provided services can be used in the 1.3 startup-sequence to speed up execution.
