Issue while attempting to run a fix script in background

[prasanna11]

When attempted to run a fix script in the background i see the below error

'Attempt made to impersonate a non-existent user: <some sys_id>, returning null instead'

What ideally happens in the background when we try to run a fixscript in the background?

[Brad Bowman]

Running a fix script in the background just frees up your client session so you don't have to sit there and stare at the progress window.  It's likely the error doesn't have anything to do with running in foreground or background, rather the code itself and the inability to run an impersonation command with an invalid user sys_id.