Spectre is telling you that there is a problem at 'I0.I51.C0.1" and 'I0._net3". There is some problem such as a floating node or loop of shorts there. When you look in that area, what do you find?

-Ken

It seems as if the basic problem still exists. There appears to be some problem in the circuit or with a model near  'I0.I51.C0.1" and 'I0._net3". When you look in that area, what do you find?

-Ken

The message "Convergence difficulties resulted in error requirements being unsatisfied." indicates that Spectre could not take a time step small enough to maintain accuracy because of convergence problems. This implies that there is some problem in the circuit that only becomes exposed with small time steps. Typically, this happens when there are discontinuities in the capacitors. With large time steps (long time periods) the capacitors are diluted with the resistive portion of the circuit. But with very small time steps the capacitive part of the circuit dominates. In the extreme, with very small time steps, the effect of the resistive portion almost disappears. In this case, the capactive part of the circuit must be simulatable by itself. Thus, the capacitor models must all be continuous and there must be capacitive paths from all nodes to ground.

You can often circumvent this problem using cmin, which adds a capacitor from every node to ground, which provides the capacitive path to ground and tends to smooth the discontinuities.

-Ken