[web2py] I get this a lot when stopping a queue mid-stream

[weheh]

When I stop my background queue job to inspect the state of the queue
records *from within web2py admin*, I often can't get to the db record
of interest because of the following error:

  File "C:\web2py\gluon\sql.py", line 1537, in __allocate
    raise RuntimeError, "Using a recursive select but encountered a
broken reference"
RuntimeError: Using a recursive select but encountered a broken
reference

Can someone explain what's happening here?