Veriloga Convergence Issues with DFF

I am using the code below for a d-flip-flop. Its basically copied from designersguide.com and modified. It seems that there are convergence issues depending on whether V(qb,gnd) is defined or not. Could you guys please provide some guidance on what might be happening here?

Thanks!

`include "constants.vams"
`include "disciplines.vams"

// d flip flop with reset (reset is active high) and parameterizable initial state
module dff2 (clk, d, reset, q, qb, gnd);

input clk, d, reset; output q, qb; inout gnd;
voltage clk, d, reset, q, qb, gnd;
parameter real v0=0;
parameter real v1=1 from (v0:inf);
parameter integer dir=1 from [-1:1] exclude 0;
parameter real td=0 from [0:inf);
parameter real tt=0 from [0:inf);
parameter integer init_state=0 from [0:1];
integer actNow, out, state;
real thresh;

analog begin
    thresh = (v0+v1)/2;
    actNow = 0;
    @(initial_step or cross(V(clk,gnd) - thresh, dir)) begin
        actNow = 1;
    end
    out = idt(0, V(d,gnd)>thresh, actNow);
    V(q,gnd) <+ transition(out ? v1 : v0, td, tt);
    V(qb,gnd) <+ v0 + v1 - V(q,gnd);
end
endmodule

"Error Report"

**************************************************************
Periodic Steady-State Analysis `pss': estimated fund = 650 MHz
**************************************************************
Trying `homotopy = gmin'.
Trying `homotopy = source'.
Trying `homotopy = dptran'..
Trying `homotopy = ptran'..
Trying `homotopy = arclength'.
None of the instantiated devices support arclength homotopy. Skipping.

Error found by spectre during DC analysis, during periodic steady state analysis `pss'.
ERROR (SPECTRE-16080): No DC solution found (no convergence).

The values for those nodes that did not converge on the last Newton iteration are given below. The manner in which the convergence criteria were not satisfied is also given.
Failed test: | Value | > RelTol*Ref + AbsTol

Top 10 Solution too large Convergence failure:
V(u65:idt0) = 0 V
update too large: | -1 V | > 0 V + 1 uV
Top 10 Residue too large Convergence failure:
V(u65:idt0) = 0 V
residue too large: | -1 V | > 5 mV + 1 uV

"