You could try a few of the usual approaches, such as
forcing more conservative solutions, using a method
like Euler that is more damped, etc. I'm almost
certain that the Cadence help docs have some of the
same advice for you.
It looks like the current shown, before it quits, is in
bursts; maybe the outer loop is unstable and you're
chopping the control voltage and seeing activity / no
activity, maybe the oscillator is killed by out of range
control voltage (that would be a bad design, or a
bad testbench).
.