Hong, I do not understand why you changed the behavior of TSGetStages_Theta https://gitlab.com/petsc/petsc/-/merge_requests/3500/diffs#a582bbaec75f4ae14bbf97d1d0404073ca89ff09_1194_1209 with this MR https://gitlab.com/petsc/petsc/-/merge_requests/3500
Now, the non-endpoint variant does no longer use th->X as stage! Please revert this change Thanks -- Stefano
