I just upgraded to 3.6.0 and my code stopped working. All dt are rejected. I used the same configure line, same code, same everything. With 3.5.4 I get: 0 TS dt 1e-06 time 0 0 SNES Function norm 2.549981005316e+05 1 SNES Function norm 6.107056905987e-03 2 SNES Function norm 1.483881932064e-10 3 SNES Function norm 9.122873794272e-11 Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 3 0 SNES Function norm 7.790429171165e+04 1 SNES Function norm 7.289068747803e-04 2 SNES Function norm 8.227639633330e-11 Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2 0 SNES Function norm 1.154356516184e+05 1 SNES Function norm 2.309925413255e-03 2 SNES Function norm 6.382141981406e-11 Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2 TSAdapt 'basic': step 0 accepted t=0 + 1.000e-06 wlte=0.000654 family='arkimex' scheme=0:'3' dt=1.000e-05 With 3.6.0 I get: 0 TS dt 1e-06 time 0 0 SNES Function norm 2.549981005316e+05 1 SNES Function norm 6.107056925316e-03 2 SNES Function norm 1.519319591792e-10 3 SNES Function norm 9.070104116945e-11 Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 3 0 SNES Function norm 7.790429171165e+04 1 SNES Function norm 6.942541792651e-04 2 SNES Function norm 8.458781909516e-11 Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2 0 SNES Function norm 1.154356516184e+05 1 SNES Function norm 2.287202942961e-03 2 SNES Function norm 6.585201377573e-11 Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2 TSAdapt 'basic': step 0 rejected t=0 + 1.000e-06 wlte= 324 family='arkimex' scheme=0:'3' dt=1.311e-07 Any ideas? I attached the full output. Options I use: -ts_view -ts_type arkimex -ts_arkimex_fully_implicit -ts_adapt_monitor -ts_monitor -snes_monitor -snes_converged_reason -ksp_type preonly -pc_type lu -pc_factor_mat_solver_package mumps -snes_rtol 0 -snes_atol 1e-10 -snes_stol 0